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Castelli Flanders Long Sleeve Base Layer

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Item # CST2700

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Item # CST2700

Layer up.

Needless to say, we get excited any time that a new item is added to Castelli's Rosso Corsa line. However, we know that our cycling love runs especially deep when that item is a base layer. In our defense, though, a proper base layer is one of the single most important pieces of winter apparel that you should own. Knowing this, Castelli created the Flanders Long Sleeve Base Layer to be its most sophisticated winter base layer to date.

To start, the Flanders base layer features multiple fabrics in multiple locations. In other words, Castelli was dedicated to applying the right tool for the job. At the body, the base layer uses a multi-denier (multi-weight) polyester composition. This material was created with a rib-knit, 3D structure that enhances mechanical moisture wicking, while also creating a stretchable, conforming fit around the torso. However, it's important to note that this design essentially creates channels that keep the fabric largely off of your skin. Ultimately, this reduces, if not eliminates, the threat of abrasion.

At the underarms, a natural evacuation point for excess core heat exhaust, Castelli placed a perforated mesh polyester. And, as you probably guessed, perforation equates to ventilation. As a result, your body temperature remains well-regulated, which prevents the threat of overheating. For the sleeves, Castelli retained the lightweight polyester theme of the base layer, only the fabric used here features a four-way stretch. This way, you're guaranteed an uncompromising freedom of movement.

Further along with the construction, you'll find that Castelli only used four-needle flatlock stitching throughout. This construction method equates to a lower-profile seam and a flat stitch. And, as a result, the base layer lays closer to the body, which makes for increased moisture management and no chafing. Lastly, Castelli sought to ensure that your body obtains total coverage, and to do so, it incorporated a mock turtle neck and an elongated back.

The Castelli Flanders Long Sleeve Base Layer is available in the color White and in six sizes from X-Small to XX-Large. Please note that Castelli recommends this base layer for a temperature range of 35-68 degree Fahrenheit.

Tech Specs

100% polyester
Recommended Use:
Manufacturer Warranty:
1 year

Size chart


Men's Apparel
 Small Medium Large X-Large 2X-Large 3X-Large
Chest  35.5 - 37in
(90.2 - 94.0cm)
37 - 38.5in
(94.0 - 97.8cm)
39 - 41in
(99.1 - 104.1cm)
41 - 43in
(104.1 - 109.2cm)
43 - 45in
(109.2 - 114.3cm)
45 - 47in
(114.3 - 119.4cm)
Waist 29.5 - 31.5in
(74.9 - 80.0cm)
31 - 33in
(78.7 - 83.8cm)
33 - 35.5in
(83.8 - 90.2cm)
35.5 - 37.5in
(90.2 - 95.3cm)
38.5 - 40.5in
(97.8 - 102.9cm)
41 - 43in
(104.1 - 109.2cm)
Hips 36.5 - 38.5in
(92.7 - 97.8cm)
38 - 40in
(96.5 - 101.6cm)
40 - 42in
(101.6 - 106.7cm)
42 - 44in
(106.7 - 111.8cm)
44 - 46in
(111.8 - 116.8cm)
46 - 48in
(116.8 - 121.9cm)
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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Needs Longer Sleeves

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

The sleeves were designed too short for a cycling garment, and are about 3 inches away from my wrists. Also, I find the high neck restrictive. I now know I prefer a lower neck base layer, so when I am hot I can unzip my jersey and cool more easily.

Nice product but........

  • Fit: Runs small
  • Size Bought: xxl

OK count me as another person baffled by the size problem. I am 6' 3" and 195 and I ordered a xxl and it was way too snug. Maybe a lot of cyclists like tight-fitting garments. Not me. I prefer comfortable, looser garments. Had to return it. Maybe they need to make a xxxl or xxxxl to accomodate folks.

Runs VERY VERY small

  • Familiarity: I returned this product before using it

I am 5'11", 155lbs, slim, and the Large was way small for me. Sleeve length and overall sleeve/torso diameter were very small and tight. I enjoy Castelli gear, and even the reviews did not prepare me for how small it would be. I am not even sure the double extra-large will fit.

I am half joking, but I wish competitive cyclist would have a suitcase full of Castelli clothing representative of all the pieces that you could rent/check out from them to find out what sizes you wore in their products. Their sizing is just so unpredictably small that it remains confusing. I have recently experienced the same things in their glove sizing which was impossibly small.

Avg. ride time: 2h 29m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Extremely small

  • Familiarity: I returned this product before using it

Im a big fan of Castelli but typically need to by one size bigger than usual. Im 6'5" and weigh 180lb and the XXL base layer would barely fit over my head, let alone my shoulders. Order at least one maybe two sizes bigger than usual .

Avg. ride time: 5h 43m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

This runs small, even for Castelli

  • Familiarity: I've put it through the wringer
  • Fit: Runs small

I'm 6'2" about 190 lbs and i could barely put on the XXL. If you are any bigger than me, i would say look for something else. I'm not exactly sure why Castelli does not have a standard sizing. I had an older Castelli base layer and the XL fitted me just fine.

Too small!

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

I ordered a medium for my husband (5'10" and 180lbs - large upper body build). When it came in he tried to try it on but could not. It was quite comical because he spent a good minute stuffing his head through the head hole and then trying to make the shirt fit...it was even funnier when he tried to get it off and got stuck half way through. What a workout just getting the shirt off and on. It was clearly too small- the fabric was basically bursting at the seams. He mentioned that maybe I should try it on before we spent money on returning the darn thing...so I tried it on (5'4" female 115lbs - small frame) and the shirt fit perfectly! It was form fitting, a little long on me, but did the trick. It really does work well as a base layer. Great at wicking moisture, yet keeping you warm. Although, even I had troubles with getting my head through the hole, though, but the positive is that my neck is very warm while riding :D

I purchase a lot of gear from Castelli (and other Italian brands like Sportful, Santini, and Di Marchi). You need to size up one or even two sizes sometimes with Italian kit makers. I know it's annoying! I am 5'10" and 190. The XL fits me well. Just enough room in the shoulders. Plenty of length in the arms. No wonder the medium was too small for your husband! Don't give up. Try the correct size. Castelli makes some of the best cycling clothing.

thanks for the comment :) I will remember that about Castelli...we're still new to the cycling world!

Avg. ride time: 1h 2m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Phenomenal wicking!

  • Familiarity: I've put it through the wringer

This base layer is spectacular at wicking, consequently I stay warm, but not overheated, on cold rides. How spectacular? At the end of a ride, this base layer is soaked, the inside of my mid-layer or jacket is damp, and my skin is dry. This is after anywhere from a 30 minute ride to a 2 hour ride, in temps from 30F to 50F. Unbelievably effective.

The only downsides are that it must be washed after every use since I'm apparently a Sweaty Betty, and the neck-hole is tight. What's the opposite of "damning with praise"?

Did I mention how good this base layer is?