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Castelli Free Aero Race Kit Version Bib Shorts - Men's


Item # CST005K

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Item # CST005K


Color the wind.

The Free Aero Race Kit Version Bib Shorts take the complex patterning, materials, and technology that make them the industry's most sought after and oft-mimicked racing bib shorts and adds something that only Castelli can: a generous splash of Italian flair. The Kit Version shorts are designed to correspond with Castelli's complementary Free AR 4.0 Jerseys, and the benefits are twofold.

First, you're not just another self-same weekend warrior wearing solid black or mismatched kit accrued from years of charity rides. Second, the pronounced styling draws attention. When you're a sub-200 pound combination of carbon, metal, and organic matter that shares the road with 4,000 pound vehicles, being as noticeable as possible is a good thing. Like the less colorful members of its family, Free Aero Race's Kit Version is designed to cheat the wind, reducing power output requirements by a claimed 10 watts at 50 kilometers an hour. The secret to these gains lies in how the shorts manage airflow across their multiple boundaries and textures — most obviously via the dimpling across the shorts' outer plane. Like with a golf ball or some deep carbon rims, these dimples manage the turbulent lamina of air that runs along the shorts' surface, preventing its premature release into pockets of drag-inducing dead air.

The Kit Version also keeps the beloved Progetto X2 Air Seat Pad, which returns from last year's version with only one, minor change: its surface is softer, which means it now presents a more gentle face to your perineum. It retains its bacteriostatic properties, seamless construction, four-way stretch, and ventilating, perforated foam layer. The perforated viscous comfort inserts also enjoy an encore performance, so your sensitive areas will enjoy riding over all manner of terrain.

Those may be the only returning features of the previous model — not even the materials used were safe from Castelli's obsessive need to tinker. The seat and front of the shorts both feature fabrics designed for durability and cooling breathability, respectively, and the entire body is 30% Lycra for a fit that strikes a balance between compression and unrestrictive movement.

The bibs' wide open, non-stifling design also returns from the previous model, but the bibs themselves now comprise two materials. The straps are mesh 3/4 of the way up, but — like any good domestique — the mesh lets a yolk of Castelli's innovative Carré material summit your shoulders. Carré is a hem-less strap that lies virtually flat against your skin, so there aren't any wind-grabbing, stegosaurus ridges from bib straps bulging out of your jersey. The liminal seam between mesh and Carré is also reinforced, so you don't have to worry about any wardrobe malfunctions while hoisting the trophy on the podium.

Last year's model featured Castelli's upgraded Giro3 integrated grip bands at the hem, but it shouldn't surprise you at this point that Castelli has upgraded these yet again. The new Giro Air has the same perfectly flat, stay-in-place grip, but with less mass, which no doubt contributes to the claimed overall weight loss of 17 grams and definitely reduces the aerodynamic footprint. The new band is wider, almost equaling the length of a typical Euro-slammed road stem, and every square millimeter of the material acts as the gripping agent. No silicone gel print here.

The lower mass means the leg bands are also pretty transparent, which may initially be a turn-off, but will likely take off as it appears in the pro peloton. In this case, it's important to note that "pro" isn't short for "UV protection," so we recommend a bit of sunscreen applied a few minutes before suiting up. As a final touch, Castelli included highly reflective details on the back of the grippers for extra safety, just in case you get caught out at a time when sunscreen won't do any good.

Tech Specs

race fit
Progetto X2 Air
yes, Carré yolk
Leg Gripper:
Giro Air
Claimed Weight:
[size large] 178 g
Recommended Use:
road cycling
Manufacturer Warranty:
30 days

Size chart


Men's Apparel
 Small Medium Large X-Large 2X-Large 3X-Large
Chest   36.2in
Waist 31.5in
Hips 37.0in
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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