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CastelliFlanders Warm Long-Sleeve Baselayer - Men's


Item # CST002W

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  • Grey, XS ($89.95)
  • Grey, S ($89.95)
  • Grey, M ($89.95)
  • Grey, L ($89.95)
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Item # CST002W

Flanders Warm Long-Sleeve Baselayer

Nothing ruins a ride faster than catching a chill. Except maybe a flat tire. Or slushy conditions. Well OK, there are lots of things that rival catching a chill, but we still don't like it. So as the seasons change, we start thinking along the lines of layers, and this inevitably leads us to the Castelli Flanders Warm Base Layer.

The Flanders is made with a durable SottoZero Fleece that insulates and wicks. Dryer, after all, is warmer. Mesh inserts provide ventilation in the underarms, just in case you overheat, and the flatlock stitching and flat hems mean the Flanders will fit comfortably as a piece of layering gear. Castelli recommends it for use in 25 to 50 degrees Fahrenheit, and, while this range may seem excessive, we find that the Flanders gets the job done in all conditions when layered with the right outer layer.

The Castelli Flanders Warm Base Layer - Men's is available in six sizes ranging from X-Small to XX-Large in the color Grey.

  • Midweight base layer designed for winter cycling
  • Multi-denier wicks effectively so you stay dry
  • High-loft fleece lining provides warmth to spare
  • Mesh armpits help prevent overheating
  • Flat-lock stitching for an irritation-free fit
  • Flat hem comfortably tucks away into your tights
  • Recommended for 25 - 50-degrees Fahrenheit
Tech SpecsSize
Tech Specs
SottoZero Fleece (100% polyester)
Insulation Weight
Recommended Use
cycling, mountain biking
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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Lightweight and Warm

  • Familiarity: I've used it once or twice and have initial impressions
  • Fit: True to size
  • Size Bought: XXL

This garment fits next to the skin and does a great job wicking sweat and keeping the upper body warm. I have a 45in chest so the XXL worked for me.

Flanders baselayer

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

It’s comfortable and very warm and great quality.
Runs really small, like almost 2 sizes small.


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

This is an amazing lightweight baselayer that really keeps you warm and dry. I’ve used it in conjunction with a Castelli Alpha ROS Jacket and been comfortable starting rides at 25 degrees.

Very Good

  • Familiarity: I've put it through the wringer

This is a very good base layer. Keeps me warm for most of my ride. However, for high-intensity rides or on rides with significant climbing, it leaves me a little chilly on the back half. Maybe the thickness? My Craft long sleeve base layer is much thinner and just as warm.

This Is just what I have been looking fo

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

Up until now, I have been combining thermal short sleeve base layers with thermal long sleeved jerseys under my Castelli Alpha jacket when it has been in the 30s. This base layer has replaced that combination very efficiently and successfully. Together with the jacket, this feels much less bulky and it is very comfortable and keeps the core at a good temperature. For rides below 30, I would probably wear a thin tank underneath.

My go to base layer

  • Familiarity: I've put it through the wringer
  • Size Bought: medium

Love this thing. It's warm and stays dry with the right layers. Soft with a lightweight material in the pits to regulate the heat. Fit is snug and I usually wear it under a size large castelli jacket in the winter.

Great Base Layer

  • Familiarity: I've put it through the wringer

Great base layer to provide extra warmth. It wicks well and keeps you felling dry. material is soft with a tight fit.

Super soft

  • Fit: True to size
  • Size Bought: Large

Yet to wear it outside but super soft. Much thinner than expected. Size is perfect. Large 6ft 175. Much more comfortable than wearing a super tight Under armour baselayer.

I just wanted to tag this on here because I don't feel I should post a rating since I never wore it out. For the record, I had to return a large because the sleeves were way too short. The rest fine perfectly fine. Not getting the XL because I think it'll be too big. I'm 6'0 163.

Perfect layer for early spring!

  • Familiarity: I've used it several times

This has been THE perfect layer to wear under my Giordana AV200 jacket for early spring riding. Feels really good for high intensity at 35-40 degrees and 40-50 degree basemile rides. Typical Castelli sizing. I'm Small in regular clothes but a full on Medium for this baselayer.

Miss you man!! Cheers. Hope all is well ride on

Super warm

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

I was looking for the heaviest, warmest base layer I could find. I wanted to wear base layer and race cut thermal jacket for down to low 40s temps. This was about all I could find that fit the bill and it’s exactly that. A slim fit, thick base layer that also breathes pretty well. It fit nicely under my Capo Thermal CC edition jacket and was perfectly warm.

This base is not even close to "thick". Its incredibly thin but somehow does the job of something much thicker, but to call this thick is simply not accurate.

Not bad

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

I wore the Castelli Flanders sz L (5'7 ; 180 lbs ; 42 chest) with a Castelli Espresso 4 jacket (sz XL). During my 1 hr road ride I had sweat on my upper back and a little bit on my tummy. Temperature was in the upper 30's hardly any wind. I opened the vents on the jacket which helped. I figure with this combination I can get into upper 20's easily with vent zippers on jacket closed. The Flanders in this size was very form fitting but not restricting for me. The inside is nice and very soft. The perforated arm holes add extra breathability. Can't give it four stars, as I just started riding late last summer and don't have anything to compare it too. Having just said that you should also take this review with a grain of salt, as I'm a newbie.

A must have for your winter kit.

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

I rarely pay full price for gear, but made an exception with this base. I needed something to keep me warm during rides into the mid 20's. This base is worth every penny. It's super soft and the mesh pit areas are great. I wore only this base under Castelli's Perfetto jacket and got cold as I began to sweat. I added a summer base under my bibs and wore this then the jacket and it's the perfect cold weather setup. Highly recommend. I wear XL in most other Castelli products and the large in this is a bit looser than I would prefer.

Great Layer

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

My brother in-law picked this up recently for some winter commuting and loves it. It fits great and will help keep him nice & warm this year.

Very comfy, very warm

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

I needed another base layer to stay warm on cold weather rides in the NY area. It's a little on the small side (which is expected for Castelli), but stretches very comfortably. It fits very snug, but is not tight. I rode in mid 40's and mid 30's, and it definitely keeps me warm. It's probably too warm above the mid 40's, but perfect for anything colder. The shirt was completely soaked in sweat after my ride, but I did not notice any dampness during the ride.

Great product.

It was exactly what I had hoped for!

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

I've got other liners that aren't biking specific but I wanted something that I could use for biking that would fit like a biking liner. I loved that this was fairly snug and that the sleeves were long enough. I often have to deal with slightly short sleeves.

Warmth was phenominal. I rode this last weekend on a night ride (12:30 - 4:00 a.m.) up to 9000 feet and it was in the mid 40s. Temp was great during the climb but I did add a windbreaker for the decent and that was enough to keep me comfortable and happy. This is exactly what I was hoping for!

Warmest base I own

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

I've now ridden probably 5-6 rides in a New York winter in this base and am very impressed. Super-warm (almost too much so!) and fits perfectly. The fleece backing makes this feel almost like a thick jersey on its own. In 30-40F temps I'll wear this under a soft-shell jacket or heavy-weight winter jersey and be verging on overdressed once I've warmed up. Note that the thick material doesn't dry nearly as quickly as lighter synthetic or merino base layers - when I've gotten sweaty in the early part of a ride I've stayed that way for a while.

Generally very happy and this has become my go-to for deep winter.

Great Great Base Layer

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

While chatting with Zach on the chat line, he recommended this Castelli base layer. When you first take it out of the box you wonder how such a thin garment could be warm. It is. Really warm. I was warm with just this and a long sleeve jersey in 40 degree weather. This is an amazing shirt. It feels like a man-made wool only softer and without any itch. I'm between a S and M in size on Castelli products and Zach recommended a M. He was right and the M is still snug but not tight. After one use I bought another one. I love it.

Does what it claims

  • Fit: True to size
  • Size Bought: Large

I have worn this top a few times in 40+ degrees and it has always been perfect. This base layer does exactly what it claims.

Perfect winter base layer

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

Very thin and light, but works incredibly well. My go-to setup for winter riding. On extra cold days, wearing a mesh summer layer underneath is a neat trick. This creates and extra layer of air pockets and improves the insulation considerably. I have washed it at least 20 times at this point and it's kept up really well. No tearing or piling of the soft inner layer at all.

Great product

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

Fit well and keep warm and skin dry for 3 hrs ride. My outer jacket however, was wet.