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Castelli Seamless Men's Sleeveless Base Layer


Item # CST2600

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  • Select options
  • White, S/M ($49.95)
  • White, L/XL ($49.95)
  • White, XXL ($49.95)
  • 100% Guaranteed Returns

  • Free Shipping

    on orders over $50
Item # CST2600


It's not cool to be hot.

If it's hot out, and you're not wearing a base layer, you're doing it wrong. A proper base layer, like the Castelli Seamless Sleeveless Base Layer, will efficiently manage moisture and actually keep you cooler.

To achieve the aforementioned, Castelli constructed the base layer from two fabrics, polypropylene and nylon. As you might imagine, the materials express a duality to the base layer's function -- pulling and drying. Accordingly, the inner-layer is comprised of the polypropylene material. This fabric effectively pulls moisture away from the skin, transferring it to the outer-layer of nylon. Why nylon? Because its lightweight, airy composition is an efficient evaporator, drying quicker than most materials. So, instead of simply soaking in your sweat, the base layer keeps you cooler by evaporating moisture next to the skin. This has been furthered by the three different mesh patterns on the base layer. Taking anatomy into account, this system maintains a consistently open mesh in order to provide the most ventilation possible. Accordingly, this keeps you cooler, as well. Don't believe us? It's time for an experiment. Blow on the back of your hand while dry, and now blow on the same spot after applying a minimal amount of moisture? Cooler right? Well, that's basically the principle behind this base layer.

The Castelli Seamless Sleeveless Base Layer is available in the color White and in the sizes Small/medium, Larg/x-large, and XX-Large.

Tech Specs

[inner layer] polypropylene, [outer layer] nylon
Antimicrobial Treatment:
Claimed Weight:
[size large] 57 g
Recommended Use:
road cycling
Manufacturer Warranty:
30 days

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.

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Here's what others have to say...

5 5

YES, must have in the Summer

  • Familiarity: I've used it several times

OK, I finally purchased this piece... This fish-net like baselayer is very effective in warm weather exactly as Blder 7 describes below. This garment is designed to keep you cool in warm and hot weather by holding your jersey off your skin. Every serious rider should own a garment like this for riding in warm weather.

This vest baselayer and a summer jersey make a GREAT combination. Your skin will be totally dry even after a hard ride.

4 5

??? ??????.

이번에 카스텔리에서 Sleeveless Base Layer를 구입했는데, 착용감이 너무 좋아 벌써 부터 여름이 기다려집니다.

절대 강력 추천하는 품목입니다. ^^

Does this base layer provide sun protection?...

Does this base layer provide sun protection? i.e. can I use it under the Climbing jersey and not worry about getting a sunburn?

Responded on

Hi Perry,
The Castelli Seamless Men's Sleeveless Base Layer would not provide adequate sun protection.
It has a very open mesh weave that would expose the skin to the sun.

5 5

Must have in summer

  • Familiarity: I've put it through the wringer

This base layer is like having air conditioning in the summer! It creates space between your body and your jersey to allow air to flow in between and cool your skin. It also pulls the sweat off your body. Makes a big difference when riding in 90-100 degree temps. I am 6'3", 195 lbs and went with the L/XL as the piece stretches and you want it to fit tight.

Responded on

B7, which is better? Castelli's "seamless" baselayer above... or Castelli's "core mesh" vest baselayer? They seem almost identical.

Responded on

According to CC, the seamless has different mesh patterns to breath better in key areas.

A better view of the baselayer

A better view of the baselayer

As you can see from the open mesh, it's nothing like a t-shirt baselayer. Looks pro with a jersey, though.

5 5

This baselayer won't overheat you

I never would have thought that a baselayer would be a good thing to have, but a crash where I got road rash on my back showed me otherwise. An extra layer might have spared me a week of road rash healing.

But...a baselayer for hot weather? Crazy! But not really. The mesh construction lets air flow freely, helping keep me cool. Most telling, my torso feels reasonably dry during the ride but when I take the jersey off it's soaked. So the baselayer transfers sweat outward.

The material's stretchy, so as small as these are they're more forgiving than they look. But don't wear these minus the jersey unless you want weird looks.