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

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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.

  • Aerodynamically-designed
  • Colors match Free Aero Race jerseys
  • Progetto X2 Chamois

Tech Specs

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

Size chart


Men's Apparel
Chest 36.2in
Waist 31.5in
Hip 37in
Inseam 31.9in
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...

Avg. ride time: 4h 51m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.
4 5


  • Familiarity: I've used it several times

These are the second pair of Castelli's new Free Aero shorts I've owned. I was a convert to the previous version, but was skeptical when I tried the new ones on (size Large) and felt like my privates were up inside my stomach. However, after a few rides they stretch out and feel more comfortable. The tightness is great when you do back-to-back long, hard rides and the second day you want a more compressed feel on your tired legs. They have a terrific look and for those who prefer a thinner chamois they are the best shorts out there.

Unanswered Question

Is it safe to follow the sizing guide for these Shorts (Castelli Free Aero)?

4 5

About the size...

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

I bought this is 3XL. I am 225 lbs and 6 ft. In comparison, I wear a XL in most and a 2XL in Pearl Izumi. The straps seem a little tight when standing, but are OK when riding, though the tend to roll. That being said, this it the most comfortable chamois I have ever had. I would buy them again.

wanted to know if the castelli logo is now printed or is it still the sticker that they had on previous models.

Responded on

It it still a red rubbery sticker on each of the legs

5 5

the gold standard for bibs

  • Familiarity: I've used it once or twice and have initial impressions
  • Fit: Runs small
  • Height: 6' 2"
    Weight: 195 lbs
    Size Purchased: XL

I have a pair of regular Free Aero's also in XL, and this "kit" version runs a little smaller. They feel a little restrictive while walking around, and the straps take a bit of negotiating the get them to lie smooth, but once you are on the bike, the fit makes sense! No slip, no riding up, no loose spots - just great support and an excellent chamois.

Responded on

If I may ask, what are your waist and hip dimentions? I'm about your same height and weight (maybe an inch taller and 5-10 lbs heavier) and am thinking of getting this bib short but not sure about sizing. (I fall in the XL category according to sizing, but everyone's weight distribution differs, hence my question.) Thanks for your review.