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Castelli Alpha Jacket


Item # CST002F

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Item # CST002F

Jacket protection, jersey fit.

As we prepare for another season of cold-weather cycling, it behooves us to pause for a consideration of winter climbing. Climbing makes you hot, so your body produces sweat. But then you hit the top, and the fast descent through cold air cools everything off — including the sweat. Since this chain of events usually means finishing a ride in clammy frigidity, confronting one or a series of taxing climbs during a winter ride is a daunting prospect. In yet another first, Castelli produced the genre-defying Alpha Jacket for just such an occasion. Your need to climb may be due to the restrictions of local topography, the desire to interrupt the monotony of winter base miles, or your own inability to just take it easy on a training ride. Whatever the case, the most immediately obvious feature that sets the Alpha Jacket apart from its competitors is also the one that addresses this, the ultimate problem of winter cycling: how to eliminate sweat on the climb without freezing.

The Alpha Jacket's thermal layer is detached from the Windstopper layer in the front, so — unlike with other winter jackets — when you unzip the shell to let in the wind, you're only exposing the thermal layer, not your bare chest or base layer. Since the thermal layer is protective but permeable, it lets the cool in evenly, all over, not just through one frigid blast at your sternum. The thermal layer is also more breathable than the outer Windstopper fabric, which means that it evacuates moisture from your microclimate even as your body creates it on the climb. At the top, you're as dry as possible, so you can zip up and descend without worrying about cold sweat on the rest of the ride. And if the climb is too hot even for the thermal layer, you can unzip it, too, allowing for even more microclimate control.

As alluded to above, that microclimate is protected by Gore's Windstopper 150 fabric, a lightweight, four-way stretch version of the venerable cold-weather armor. The Windstopper 150 — like all fabrics that bear the brand name — is quantifiable as literally windproof, a status awarded according to air permeability testing. While the DWR (Durable Water Repellent) treated Windstopper keeps the elements out, the thermal layer beneath relegates moisture and internal temperature. Unlike typical winter jackets, it adapts to the needs of base-mile grinders and out-of-the-saddle climbers mid-ride. Castelli bills the Alpha as a three-layer piece, but it's much more lightweight, flexible, and non-bulky than a traditional three-layer jacket.

The Alpha features a raw edge at waist and wrist, an innovation that has been showing up on top-end gear in the cycling industry lately. Raw edges mean that hem and cuffs don't have elastic inserts, so they won't restrict movement or bunch uncomfortably while you move in the saddle. No more tugging at the rear flap of your jacket; it slides up and down your body as you sit up to noodle or tuck into the drops, maintaining coverage. Since the cuffs lay flat, they fit under gloves without having to stuff a bunched-up elastic into the wrist of the gloves. The lack of elastic also means that there's no compression point caused by an additional hem; the fabric itself is what keeps the jacket in place, and it keeps it in place relative to the position of your body, not just the highest point the hem has worked its way up to.

We've covered the functional aspects of the jacket, but we've been referring to it as a "jacket" this whole time, which is a bit misleading. Since the Alpha Jacket actually fits and feels more like a jersey, we'll chalk this inability to accurately classify it up to an insufficient and artificially categorizing language for describing cycling clothing. We can only assume that Castelli opted for the word "jacket" to stress the protective, layered elements of the Alpha, which are indeed on par with Castelli's jacket-iest jacket, the Elemento 7x(Air). Like the Elemento, Castelli rates the Alpha to stay comfortable from 53 degrees Fahrenheit down to freezing. We're confident, though, that five minutes in it will disabuse any cyclist of the assumption that this is purely classifiable as a jacket.

The aggressive cut of the Alpha Jacket fits jersey-close to your body, from the hem to the collar and everything in between. In previous generations of winter wear, this has been a significant put-off for us, as we're wary of sacrificing comfort for a streamlined fit when winter cycling means that comfort is already at a premium. But with the cut of the Alpha, the only spot you'll notice some uncomfortable restriction is across the chest, and only while you're on foot. Once you get on the bike, the Alpha is designed to accommodate your arms, shoulders, and back as you reach for the handlebars, courtesy of the unsurpassed four-way stretch Windstopper fabric, but there's no bulge of excess jacket hanging off your front while riding. The collar is cut so that it doesn’t create a wind chute behind your neck while you're in the saddle, and the shell and thermal layers' respective zippers are offset to eliminate any additional bulk that the Alpha's functional flexibility may entail. It has three rear pockets and a zippered pocket in the rear and the front.

The Castelli Alpha Jacket is available in six sizes ranging from Small to XXX-Large in the colors Black, Laurel/black, Lime/black, and Red/black.

  • A cycling jacket for cold, rainy weather
  • Windstopper 150 membrane blocks wind and water
  • Incorporates insulating thermal midlayer
  • Race fit eliminates flapping material
  • Offset zippers allow for micro-managed protection
  • Maintains breathability during hard efforts
  • Raw-cut hem and cuffs create a flat seal
  • The most protective of Castelli's revolutionary all-weather race kit

Tech Specs

Windstopper 150
Windproof Rating:
<1.0 cfm
fall, winter, spring
race fit
waist (with drop back)
rear, underam
1 zippered front, 3 rear
Claimed Weight:
[large] 381 g
Recommended Use:
cold-weather cycling
Manufacturer Warranty:
1 year

Size chart


Men's Apparel
Chest 36.2in
Waist 31.5in
Hip 37in
Inseam 31.9in
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.

Reviews & Community


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Great shoulder season jacket

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

I have owned the Alpha for a couple seasons now. With a thin base layer of capilene, the jacket is perfect for 35-45 degree days in rolling hills outside Boston where you are always fluctuating between climbs long enough to cause a sweat and descents steep enough to give a chill, especially on raw blustery days. I agree with Castelli that it can be worn up to 53 degree days but in the 45-55 degree range, I would rather wear something lighter. Durability has not been an issue so far.

I like the fit; it is snug but comfortable. I suspect recreational folks who have never raced might say its too tight. But for those of us in the great middle, I think it works well.

Great Jacket

  • Fit: True to size
  • Size Bought: Extra Large

I love my new Alpha for reasons which are cosmetic as well as functional. The jacket fits true to size with a little room for my base layer and jersey. It is a great winter addition. The look is great and the red stands out during the times I'm in traffic.

Unanswered Question

none of the example colours show the back of the jacket. Is the lime/black Alpha lime on the back????

Loved the jacket

  • Fit: Runs small

I reordered the xxl I always have worn xl in Castelli and Assos but this fit just a little more snugly than I like. I still liked the way it formed to my shoulders and stomach. 6ft 170lb

The Alpha construction and resulting insulation sounds similar to wearing a Gabba 2 long sleeve over a thermoflex, or similar, ls jersey. Am I wrong?

Interesting question. Castelli is based in the Italian Alps (Dolomites). They are experts at cold weather cycling. And they make a wide selection of jackets (almost confusing) to cover every temp range and weather condition one might reasonably encounter on a road bike.

So, you are correct, the Alpha jacket and the Gabba 2 long-sleeve are somewhat similar garments. They both use DWR treated Gore Windstoper textile in the body, back, and arms -which is windproof and highly water resistant, yet breathable and aero fitting. The main difference between the two jackets is that: (a) the Alpha has an "internal vest" -useful when climbing in cold weather; (b) the textile in the Alpha is slightly thicker (Gore 150 vs Gore X-Lite); and (c) the Gabba has a very breathable textile under the arms (nano flex) to vent sweat while riding at tempo in the 45-55° range. Thus... Castelli officially rates the Alpha for use between 32-53° F; while they officially rate the Gabba 2 for use at slightly warmer: 43-59°. (Btw, I would use a quality, light wicking baselayer underneath when using either -like by Craft or Castelli). Hope this info helps.

I'm going answer my own question. 34 F this morning, decided to see if LS Gabba2 could handle it. Underneath I had a Castelli SS mesh (which I wear 95% of the time summer or winter), Gore thin turtleneck BL, Nike mid weight BL. Perfect. So given the brilliance of the Gabba and various layering options I don't see a need for a separate aero jacket (Alpha) until it gets to freezing or below, at least on rides with some energy expenditure. And I can't keep the feet or face warm in those conditions anyway so stay on the trainer when it's below freezing. So I'd say if you have a LS Gabba you have all you need down to 32F or so.

Avg. ride time: 9h 52m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

What is "cold"?

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

Best jacket ever worn. Ridden @ and below freezing temps and ended up breaking a sweat.

Very good but not the best

  • Fit: Runs small
  • Size Bought: Small

Runs a little colder (and smaller) than the Assos Bonka Cento. I wear this jacket into the 40s, but reach for something warmer for the 30s. The neck pinches a bit in a size Small, whereas the Assos doesn't in the same size.

Avg. ride time: 4h 47m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Keep warm

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

If you think you are an XL then purchase a XXL. The jacket runs tight like all Castelli products. Cant say enough good things about the jacket. I wear a base layer and a Jersey with the jacket in below 32 degree weather and stay nice a warm the entire ride. If you are riding with high intensity you may get a bit warm and sweat. For those long endurance rides in winter this jacket is well worth the money.

Best Winter Jacket

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

The fit is perfect and construction is good. I've ridden in 30 degree weather with no problems at all. Warmest jacket I have ever owned! Some reviewers mentioned wet cellphones in their back pockets. I too have experienced this, but if you unzip the upper portion of the jacket to allow air to flow through ... problem solved. Happy winter riding.. :-)

Avg. ride time: 8h 12m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

great winter jacket

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

very happy with this winter jacket, and happy i splurged for it. with the right base layer (i use castelli wool LS base layer) you can ride in 30's. the only downside is that anything you put in the rear-pockets will get wet. poor venting, just be mindful i.e. put your phone in a ziplock

Great jacket, but deceptively warm

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

The fit is true to the Castelli size chart. I have a 39" chest, so I ordered a size Large, but all of my other measurements would place me in a Medium. (A size Medium might fit me, but when I tried a Castelli Elemento 7X Air jacket in size Medium the arms were too tight in the forearm/elbow area and the Competitive Cyclist salesperson said the fit of the Elemento and Alpha are very similar.) When zippered up, it's comfortable in the riding position, not walking around. It's very well made and the fabrics are high quality.

The jacket feels light but is deceptively warm. I've worn this jacket on two 2-hour (41-mile) rides in 47F and 45F weather. No climbs and moderate gusty winds. On the first ride I wore a Craft short sleeved polypro base layer t-shirt underneath it. I was far too warm after 15 minutes and completely unzipped the outer jacket. Even with the jacket front open, I was still uncomfortably warm and when I took the jacket off after the ride, the back was soaked with sweat. On the second ride, I wore just the jacket, no base-layer. Again, I felt myself heating up after 15 minutes so I completely unzipped the outer layer. Doing so made for a comfortable ride temperature wise, but the flapping of the unzipped outer jacket layer was annoying.

Given my overheating experiences, I'll only wear this jacket when the temperature is below 40F. (It's far too warm for the upper end of the 32F to 52F mfg recommended temp range.)

For me, the best aspects of the jacket are its comfort and light weight feel when riding. It's very warm but not bulky and there's no feeling constricted by layers. And the waffle-construction interior layer wicks perspiration well.

I've now worn the Alpha jacket a few more times including today in 32F, grey sky, constant wind and snow flurries. I wore a Craft SS polypro t-shirt (mentioned above) underneath it and was comfortably warm. (On my legs I wore Mavic Inferno tights.)

Yet another update,
I've now worn the Alpha jacket several more times including in air temp. down to 25F. With this jacket, temp. ranging from 30F to 40F require only a short sleeve base layer. On the rides below 30F I wore a Craft Active Extreme Concept long-sleeved base layer and was comfortable. (I also wear Mavic Inferno bib tights, Castelli CW 3.1 gloves, Assos Fugucap, and Gore Thermo shoe covers.) In temp. above 40F, I wear a Castelli Gabba II long-sleeved jersey.

Great When Layered Appropriately

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

For me, this is not a jacket I would use for PA winter riding in +10 mph wind. I live and ride in Lancaster County, PA with picturesque, rolling Amish farm land. I would describe our weather in the winter as a damp cold.

I am 5'10', 165 lbs. and 40.5" chest. The XL fits perfect in Castelli clothing.

I purchased both the Espresso 3 and the Alpha. I tested both jackets today in 40 degree weather with 12 mph wind. I wore a medium weight craft base-layer. Both jackets are superb build quality.

The Alpha is a great concept. I like the idea of the separate, thermal zip up layer. Nice, but I found myself being cold in the arms and chilly elsewhere. Aggressive riding up and down rolling hills did not increase the comfort. Maybe I should have layered with a jersey.

I came back and switched to the Espresso 3. Same base layer but what a difference. I was toasty warm and had to open up the vents. Very comfortable. As it gets colder, I can even layer a wool zip up - close fit but still very comfortable.

For me, I see the Alpha being used for riding between 50-60 degrees - unless I get a larger size and layer up. But I think that defeats the purpose and functionality of the piece. I like being comfortable when I ride. I want a jacket with a "slim" profile that keeps me warm and vents the sweat so I don't get clammy. The Alpha will definitely keep you from getting too clammy but you may find, as I did, your arms get too cold and you just feel a little chilly for a 40 degree ride.

For most cold weather riding though, I see me using the Espresso. But what's up with that media pocket???

Time will tell. Everyone's experience will be different based on metabolism, body type, topography and riding style.

I opt for comfort every time. When I'm comfortable, I will stay out longer. For the right conditions, the Alpha is a great choice. For cold weather, windy conditions I will be reaching for the Espresso.

UPDATE 11/27/15: I purchased the Castelli merino wool base layered under the Alpha . . . . what a difference! I'm able to wick away the sweat, and stay warmer than when I used the Craft base layer. For me, the wool made a big difference paired with the Alpha.

More than meets the eye. Great Buy

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

While pitched as climbing kit, this jacket is more and less than that. Confused? I was too when i got it in the mail. I put my base and a jersey on before the jacket and it was snug. So snug I took the jersey off and just rode the jacket and base. PERFECT! Look at the pictures on the web. No jersey shown. So is the 'jacket' really the world most versatile and expensive two layer wind-stopper jersey? I don't know. I do know it fits between my Espresso 3 and my windbreaker just right.

Avg. ride time: 43m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Best winter jacket

  • Familiarity: I've put it through the wringer

Great winter jacket. Very comfortable on the bike. I really like the inner panel for controlling temperature. I think that feature makes it very flexible in how you use the jacket. The wind block material is very effective and in many cases I wore a short sleeve jersey under the jacket and my arms were fine. The longer back panel is a nice feature. It does fit to the small size. 6 ft and 210 and the xxl is tight around the middle (but what isn't)

All Winter jacket

  • Familiarity: I've put it through the wringer

I rode all Winter with this jacket and just a base layer under it. I was comfortable into the 20s and added the sella rain jacket over it in the teens for extra wind protection. This jacket is amazing. I am 6'4" 195lbs and use a 3XL so be prepared for a tight fit if you aren't thin.

Alpha Jacket

  • Familiarity: I returned this product before using it

This was my first Castelli purchase so I didn't know what to expect. When I received this item I tried it on and... I actually had to try multiple times because I thought I was doing something wrong. It didn't fit at all. I'm 5'11 and about 163. I got the large. The jacket was so small I couldn't even zip it. From what I was told Castelli can sometimes be like that with the inconsistency of their products. I would have liked for this to work, but at this time I just can't recommend Castelli products.

Italian sizing. You need to size up +1 with Castelli jackets. Always.

Avg. ride time: 1h 55m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Alpha Jacket layers

Castelli bills the Alpha as a three-layer piece, but it's much more lightweight, flexible, and non-bulky than a traditional three-layer jacket.

Alpha Jacket layers
Avg. ride time: 1h 55m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Alpha Jacket thermal layer detail

The Alpha Jacket's thermal layer is detached from the Windstopper layer in the front, so — unlike with other winter jackets — when you unzip the shell to let in the wind, you're only exposing the thermal layer, not your bare chest or base layer.

Alpha Jacket thermal layer detail