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Active Cooling Sleeveless Baselayer - Men's

5 out of 5 stars
2 Reviews
Color:Silver Gray


Size Chart


Active Cooling Sleeveless Baselayer

On the hottest days, we need every trick in the book to stay comfortable on the bike: frozen bidons, pre-soaked cap, frequent shade stops. Castelli’s Active Cooling Baselayer adds to our arsenal of hot-weather techniques with innovative fabric to keep our temperature well-regulated through tough conditions. Castelli uses Polartec’s Delta knit fabric, which combines hydrophilic and hydrophobic fibers to regulate the drying for better evaporative cooling. Rather than the baselayer drying immediately, it’s a steady drying so you can benefit from the evaporation of sweat and ride harder and further in hot weather.


  • Lightweight baselayer to stay cool on hot rides
  • Polartec Delta fabric regulates drying for evaporative cooling
  • Sleeveless design lays flat under jerseys
  • Pairs best with a breathable jersey, like Castelli's Climber's or Superleggera
  • Item #CSTZ7AA
Polartec Delta cooling fabric
Claimed Weight
[large] 3oz
Manufacturer Warranty
1 year

Overall Rating

5 based on 2 ratings

Review Summary

1 Stars - 0 reviews
2 Stars - 0 reviews
3 Stars - 0 reviews
4 Stars - 0 reviews
5 Stars - 2 reviews

Fits Small

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Runs smallTrue to sizeRuns large

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5 out of 5 stars

August 4, 2021

Great base layer

I've put it through the wringer
Size Bought:
6' 1"

I find this base layer works really well especially on hot days. I like the feeling of support it gives in addition to the technical transfer of moisture away from the body. It works really well. If you're not a slim Italian size up

Simon W
5 out of 5 stars

June 22, 2020

Great for summer heat

I've put it through the wringer

I've been wearing undershirts on hot summer rides for years and have experience with a lot of different ones. These Castelli ones are my favorites so far, I liked it well enough I ordered a second one so I can spare myself a daily wash routine. The fabric is light and the cooling qualities seem to work well, even in humidity. I don't know if the cooling is light years ahead of other base layers, but I do like the way it seems to work with jerseys that also have some venting in the fabric (as most do these days). It's Castelli, so up one size from your usual (I've worn XL in Castelli since my first jersey), this fits the same as other tops I've purchased from them.


Originally reviewed on Backcountry.com