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CastelliAlpha Ros Jacket - Men's

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Item # CST00IC

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Item # CST00IC

Alpha Ros Jacket

Cold-weather cycling creates a conundrum. Naturally, we want to stay as warm as we can but if the jacket doesn't breathe well and we get too hot, we'll begin to sweat. This isn't a good thing especially if we start descending and the wind chill cools our damp jacket. To truly stay comfortable, it is imperative to have something that keeps the elements out yet regulates body temps. Leave it to the wizards at Castelli to produce a piece of kit that defies our expectation of what we know of a winter jacket. The Alpha ROS Jacket is ready for Rain Or Shine and is there to help make all of your winter rides more enjoyable. What's really nice about this jacket is that it works so well, it inspires us to go ride even in the worse conditions.

The Alpha ROS Jacket's two-layer construction separates the thermal insulation layer from the wind- and waterproof outer shell. A double front opening to diffuse the cold air when you open up to ventilate on the climbs and prevent overheating. The thermal layer is breathable and is able dissipate heat easily so temperature regulation is an all over affair and not just confined to small pockets. If things heat up even more, the thermal layer can also be zipped down. By crating two layers, each can do their job more efficiently. The thermal piece adds warmth and is more breathable while the outer Windstopper fabric keeps you dry and keeps the chill out. This results in you being less clammy at the top of the climb, and with a quick zip up, you can descend shiver-free since you'll be warm and dry.

By using Gore’s new Windstopper light rain-resistant membrane and DWR treatment, selective seam sealing, careful seam placement and construction, and a waterproof YKK Vislon zipper the jacket is essentially waterproof without compromising characteristics making it such a great dry-weather jacket too. No matter the weather report or what kind of ride or training you have on tap, this jacket pretty much guarantees a dry and warm experience.

The Alpha ROS features raw edges at the waist and wrist—a trend defining top-end gear in the cycling industry of late. Raw edges mean that the hem and cuffs don't contain elastic inserts, so they allow for complete freedom of movement and fit nicely under gloves' cuffs. The jacket never rides up, so no tugging it back into position if you have spent time doing an interval in the drops and now you are recovering on the tops.

The fit of the Alpha ROS Jacket is actually more akin to that of a jersey. Since it does come with its own thermal layer, base layers of varying degrees, depending on the temps, can be employed customizing the jacket to the conditions. Castelli rates the optimum operating temperature range between 23- to 50-degrees Fahrenheit. The Italian brand is typically conservative with its temperature estimates, so that huge range speaks volumes for the jacket's versatility.

The Alpha ROS Jacket's aggressive cut rides very close to your body. Stretch fabrics with advanced patterning make for an excellent snug fit that still accommodates a wide range of body types. You will notice a tighter feel across the chest when off the bike; however, once you're clipped in and rolling, the Alpha ROS is designed to accommodate your arms, shoulders, and back as you reach for the handlebars, so there's little or no bulge or baggy material. The articulated collar is cut to prevent wind from catching it, and the shell and thermal layers' zippers are offset to eliminate bulk and allow easy access on the go. It has three rear pockets and a zippered pocket in the rear and the front.

  • A next-generation cycling jacket for cold and wet weather
  • Windstopper 150 membrane blocks wind and water without stifling
  • Insulating thermal midlayer zips separately for targeted warmth
  • Race fit eliminates flapping material during tempo base miles
  • Maintains breathability to manage moisture during hard efforts
  • Raw-cut hem and cuffs add comfort and improve fit
  • Castelli's revolutionary all-weather race kit continues to evolve

Tech Specs
[membrane/laminate] Windstopper 150, [face fabric] 100% polyester, [liner] 90% polyester, 10% elastane
Waterproof Rating
double front opening
3 rear, 1 zip side
rear pockets
Recommended Use
road cycling
Manufacturer Warranty
1 year


Men's Apparel




















































How to Measure:
For best results, take measurements over your underwear.
Measure under your arms, around the fullest part of your chest.
Measure around your natural waistline, keeping the tape a bit loose.
Measure around the fullest part of your body at the top of your legs.
Using pants that fit well, measure the crotch seam to the bottom of the leg.

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    Great jacket

    • Familiarity: I've put it through the wringer
    • Fit: True to size
    • Size Bought: Large

    I bought this jacket on a friend’s recommendation even though it was a little pricier than alternatives, but it was worth it. It is a great jacket!

    True to size ?... Are you serious...these are a great jacket but I had to size up for mine to fit...

    Beautiful jacket, great quality!

    • Familiarity: I returned this product before using it
    • Fit: Runs small
    • Size Bought: Large

    Great jacket only thing they run real small got a large but it was very tight hard to zip. I returned and waiting for an xxl. Other than that it's a great looking jacket made with quality materials, should get my replacement on Thursday and we'll see how it fits and take it for a spin!

    Fantastic jacket

    • Familiarity: I've used it once or twice and have initial impressions
    • Fit: Runs small
    • Size Bought: XL

    As others have mentioned, runs small like all Castelli. I wear XL for jerseys, same for this jacket. I’m 5’11 and 160lb, 33 waist. Used the jacket once so far and it was perfect for the 38 degree temp when I started with nothing but a base layer shirt underneath. I love the interior vest that is built into the jacket, this provided just the right level of warmth. By the end of the ride, I was a little hot when the temp reached the low 50’s, but being able to unzip and still have the vest was a huge advantage. The quality of this jacket is amazing, and the cut is absolutely perfect. I plan on using this jacket in the 30-48 temp range in the future.

    Awesome winter jacket

    • Familiarity: I've used it once or twice and have initial impressions
    • Fit: Runs small

    I was deciding between this, Assos winter jacket, and Assos Ultraz jacket. I am extremely happy I ended up with this. It is very versatile - I rode 40 miles in it today and temps were between the high 30s and mid 40s and I was never cold (Assos winter base layer underneath). Wind was constant at 10-15 mph and I never felt it due to the awesome Infinium material. During a few efforts I heated up, but because of the inner vest, I was able to open the jacket half way to let some heat escape without getting cold. If you are considering this jacket and Assos’ offerings like I was, I’d say that thermally, this is between the Winter and the Ultraz. The Ultraz is really thick and insulated. Size wise, I am an XL in Castelli’s race fit jerseys and the XL in this fits me well. Initially, I did feel some tightness in the armpit area, but after I rode in it for a few minutes that feeling completely went away - almost as if I had to break it in a little. Finally, Castelli, I do have a few minor nitpicky suggestions if you read these reviews: I’d make the cuff a little tighter so it doesn’t bunch under gloves, use the two rear pocket concept on the back like the perfetto/Gabba line, and use the same style of zipper on the front pocket as you do for the internal vest so it lays flush with the jersey instead of dangling.

    Anyway, if your considering buying this jacket for winter riding, just do it. You won’t be disappointed.

    This is an amazing Jacket

    • Familiarity: I've used it several times
    • Fit: True to size
    • Size Bought: Medium

    This thing is fantastic. It fits exactly like all the other Castelli items I have owned. It is meant to be worn riding; not standing around. You wouldn't want to wear this as a casual jacket. However, worn properly while riding, the jacket is fantastic.

    Great mild winter jacket

    • Familiarity: I've used it several times
    • Fit: True to size
    • Size Bought: Large

    I've worn this several times now and I've really enjoyed it. The fit is quite snug for me, and feels too tight when I'm not riding and fine on the bike I think that helps for wind resistance but I might purchase an XL next time. The style is great too. Only complaint is that the elastic band in the back came unglued from the fabric after my first ride.

    With a base layer, for me this jacket is best from about 26 to 44 degrees.

    Just what you need!

    • Fit: True to size
    • Size Bought: small

    If the cold weather usually doesn't discourage you from riding then this is for you. I have worn this one in temps as low as the mid 40's and it does the trick. Climbing should be kept to the low 50's and lower. Unzip the outside layer at the bottom. you may need to unzip the inside layer to some level part way up the hill. Depends on the grade. It is a fitted cut. just enough room for an under layer or race fit jersey.

    Castelli Alpha RoS

    • Familiarity: I've used it once or twice and have initial impressions
    • Fit: Runs small
    • Size Bought: XXL

    Wore this jacket on 1st ride in a cool (high 40s-low 50s misty, drizzly (Drist?) day and was very comfortable- warm, dry, no water penetration. Fit is, as most know, extremely far of the US fittings- I'm 5'8", 175 and I had to buy an XXL. Whatever. However . . . the stitching on the back, central pocket seam came loose so I called CC and they sent out a 2nd replacement jacket with no questions asked or resistance of any kind. Great jacket, and a great company!

    Small and bunches in the arm pit

    • Fit: Runs small

    I’m 6’ 185lbs. Purchased the XXL which fits fine other than in the arm pits. (Others have mentioned this) Very uncomfortable while standing. The only time it’s not bunched up and squeezing my underarm is when I’m ™in a riding position, bent over and arms outstretched in front of me. I haven'€™t worn it on a ride and Im not sure I will. There must be other winter jackets that are comfortable in the riding and standing positions i have a couple of Endura jackets that are great. Should probably stick with them

    Small and bunches in the arm pit

    Try XXXL. I wear an XXL and tried the XXXL and found the body fit was okay but the sleeves were too long and the neck too wide.

    Joseph, I look at that jacket on you and think it is too large. I'd go a size down

    Hey Joseph, it’s definitely a race cut and meant to fit perfectly in the riding position. Oh, and I agree with Philip - you’re definitely wearing a size or two too big compared to how Castelli designed it to fit.

    Yes, the jacket should fit tighter on you. I have the Alpha ROS jersey as well and the fit should be snug. On the bike you do not know it is there.

    Assos ros alpha

    • Familiarity: I've used it once or twice and have initial impressions
    • Fit: Runs small

    I’m average size guy and the xxl fits nicely. I tried the xl and it was a little tight around the armpits. I’ve used several name brand pieces of riding gear and this jacket is very nice. Rode today in 40 degrees, cloudy with light wind. I’m using Assos mille s7 tights (m) which are also outstanding! I did need a long sleeve base. I used the craft (m) and never got a chill. I’m not sure I completely agree with the breath ability thing. My base layer was pretty wet but not uncomfortable.

    I’m 5’9” 180 with a 33 inch waist, 32 inseam and wear a 40 dress jacket. Buying without trying things on can be tough. Hope this helps.

    Castelli Alpha Ros Jacket

    • Familiarity: I've used it several times
    • Fit: Runs small
    • Size Bought: XXL

    First, regarding fit, I am 5' 7" and 163 pounds (body mass index of 25). The average BMI for an adult male in the U.S. is 26 and in my opinion, the Alpha Ros jacket is not sized for the average-sized cyclist but one much leaner than average. Almost all of the reviewers that I read (see below) sized up from one to three sizes larger than their normal size. So, I followed the many reviewers' claims about the jacket running quite small and I went up 2 sizes (I normally wear Large). For me, I made the right choice. The jacket fits snug but not too tight. Others should choose size based upon preference.    
    Here are the numbers of cyclists of each size of the 33 reviews that I could discern (from Amazon and Competitive Cyclist/Backcountry).
    Small - 1
    Medium - 4
    Large - 9
    XL - 11
    XXL - 5
    XXXL - 3
    One can see that a full 60% of reviewers of this jacket chose either a L or XL size. Plan accordingly - this jacket runs very small.
    Secondly, concerning functionality I had initial doubts whether a decidedly winter garment without much bulk could provide the essential warmth and protection for which I was looking. The first time that I wore the jacket was at 25 degrees with a base layer and jersey and it worked quite well. At that temperature riding at 20 mph, the wind chill was a bone-chilling 11 degrees. In fairness, Castelli rates the jacket as effective down to 23 degrees. Subsequently, I wore it on several 2 to 3-hour club rides in 30 to 40-degree weather with a single base layer and it effectively blocked piercing cold wind and kept me warm. I feel that it works because it is made with technologically-advanced fabrics. I like the two-piece design in which the windproof outer layer can easily be unzipped to the breathable thermal insulated inner layer when needed to vent some upper torso heat  In my opinion, this design to regulate inside heat is one of the most important features of the jacket.    
    Third, I also like the garment design around the neck because it provides additional protection and the three rear pockets and side pocket are all useful. Moreover, the cuffs are well-designed, allowing gloves to easily fit over them and seal off cold wind from entering up through the jacket sleeve. I opted for the red/black Alpha Ros color because it should be highly visible to motorists, it is a welcome addition to my standard mostly-black cycling gear and it is aesthetically pleasing.    
    Lastly, the jacket is expensive but it appears very well-made. I consistently ride throughout the year with a local cycling club and have logged more than 7000 miles on the road in 2019. I fully expect this jacket to help me withstand our 5-month winters for years to come. It does the job and I am glad that I purchased it. I rate it five stars.

    Amazing jacket

    • Fit: Runs small
    • Size Bought: XL

    It's magical how a jacket with so little bulk can keep me so warm! So far, I have worn it down to 35F (measured on the gauge built into the Garmin 1030) over just a turtleneck Flanders base layer, with zero indication that it was anywhere near its lower temperature limit. The two-zipper system works exactly as claimed: unzip the outer zipper approaching an uphill, zip it back up going down the other side, prevents overheating and sweating. The ends of the sleeves are very glove-friendly, a big plus.

    The outer zipper was slightly balky when pulling it down from the top so I applied zipper lube to the top few inches.

    A small improvement would be to make the inner thermal layer removable (zippers?) so one could clean it without having to wash the entire jacket.

    I am XL in all Castelli tops and and XL in this fits me perfectly.

    Its $350 list price seems steep until you have used it. Then it seems worth every penny. Still, I was pleased to get mine on sale!

    way too small

    • Fit: Runs small

    Jacket is well made but way too small. Went with one size larger and it is still too small.

    Best cold weather cycling jacket.

    • Familiarity: I've used it once or twice and have initial impressions

    What took me so long to get this jacket??? Had my first ride a few nights ago and was in 40's. Perfect. Did second ride with it today with just the jacket and a light, long sleeve base layer. Was about an hour from home when unexpectedly a cold rain came. The temp was a little warm for the jacket today, 53 F, but was SO glad I was wearing it. Dry as a bone and warm. At least from waist up. During first half of ride climbing was a bit warm, but easy to cool down with the two layers.

    I usually wear size Small..have 36" chest, but got the medium and it's a perfect fit. Did try a small but too tight in armpit area..otherwise good. The medium comfortably allows for heavy base layer when needed, and even jersey as well if it gets freezing. Tried the Assos too, and prefer the Castelli for both fit and function.

    Will use for both road and mountain biking. Got it on sale for about $220. Would I spend the full $350 for it? Well, it's worth it, but probably would suggest getting on sale. Now I definitely need waterproof booties!

    Flexible and warm

    • Familiarity: I've used it several times
    • Fit: Runs small
    • Size Bought: XL

    Excellent piece of kit, seems well made And can be made useable in warmer temps and colder temps 30-50f. Great jacket and worth the price, almost too warm in the high 40-50f temps but can be easily unzipped to add some cooling. Nice color options as well the orange color is very visible while being stylish and not the typical high vis yellow.

    Super warm jacket!

    • Familiarity: I've used it several times
    • Fit: Runs small

    Crazy how a jacket so thin keeps you so warm! The technology these days is amazing. 45 degrees with no sun is pretty much the upper limit I think for this jacket. I first used it at 31 degrees and it kept me warm, by the upper 30's to low 40s, It really blocks the icy air when going 20 - 40+ mph. I had the inner base unzipped and had the outter shell partially unzipped so as to not sweat too much. I am 6 feet tall and around 182. based on other reviews, and body dimensions given, I chose the Large, it fit very well except for the armpits. It dug into them even when I test road in front of the house, I went to XL, same thing happened, so I went to XXL and the jacket fits perfectly. I must say, I didn't see much in size change with the 3 jackets other than it felt more comfortable now. Still conforms to the body and is sleek. It works like a regular jersey with the 3 pockets in the back, and it has a zipper pocket in the front as well. Comp Cyclist was awesome, I would exchange and have another jacket in 2 days each time I had to re size.

    Amazing jacket!

    • Familiarity: I've used it once or twice and have initial impressions
    • Fit: Runs small
    • Size Bought: 3XL

    Absolutely love this jacket. I have worn it only once in 46 degree temp in 12-15 mph winds. I only had a short sleeve base layer t-shirt underneath and was more than comfortable. Prefect Castelli fit.

    Alpha RoS jacket

    • Familiarity: I've used it several times
    • Fit: Runs small
    • Size Bought: XXL

    I've worn this jacket twice: 1st- 46 degrees w/ light drizzle to light rain. I was not only warm but also dry; 2nd- mid 50s with cool-cold breeze. I opened the jacket zipper on climbs, arms were a little warm but fine. So far I am very impressed. I wear my Pefetto jersey on 50s temp rides and now I'll wear my RoS jacket in low 50s and below. I really like both jersey and jacket.

    The Best Kit

    • Familiarity: I've put it through the wringer
    • Fit: True to size
    • Size Bought: Large

    Usually buy Castelli. Sizing is perfect. Race cut with performance in mind. It is warm. It is form fitting. It sheds water. I am extraordinarily picky with cycling kit. And this is the best piece of cycling kit i have ever worn. If you knew me, you would know how big of a deal that statement is. So, if you plan on pedaling hard, you are performance oriented, and you care about style, form factor, comfort, and having everything while sacrificing little to nothing, then this piece is for you. If that is you, then get this. As far as Castelli sizing goes, this is not too small. True to size.

    Nice review. A request to all reviewers: it's a great piece of kit, but what are all your sizes if you have not mentioned them? It greatly helps others to mention your suit jacket size (ie, 40, 42, etc), height, weight, sleeve length, neck, and if you're long-waisted (and do you prefer to wear "Tall" sizing in shirts), etc. What I'm getting at: is this jacket long enough in front/back/sleeves? Is it too snug, too big or just perfect in neck, etc.? Grazie Mille.

    Well-made jacket

    • Fit: Runs small
    • Size Bought: Large

    I bought this jacket near the end of the winter season, but had the chance to wear it under race conditions. The jacket was everything I hoped it would be. It fit snugly (fit advertised to run small) but not too tight; it felt almost like a second skin. I was comfortable throughout the race (28-35°F) and the fabric shed the falling snow easily. The zipper was easy to operate with gloves on and the front zipper pocket was handy for food. The inner vest provides protection when the main zipper is used to control body temp. Very happy with this jacket!