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Item # CST2610

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Item # CST2610

That's a lotta sock!

The Castelli Free 9 Sock is woven with Meryl Skinlife antibacterial fibers. This moisture-wicking, breathable fabric pulls sweat away form your skin to keep you dry and comfortable. The top of the foot is a diaphanous web, ultra-thin and extremely breathable. In the middle of the foot, the arch area, there is a high-density band woven in. You won't notice any difference in thickness, but you will feel like the sock is becoming one with your foot rather than sliding around between your foot and your shoe. The toe has a flat seam for comfort and the cuff at the top is folded over to keep the sock from slipping. Castelli also added an open mesh panel to the cuff to allow air to move freely through the sock.

The Castelli Free 9 Sock comes in three colors: Mandarin, Ocean, Red, and White. Sizes are S/M, L/XL, and 2XL.

  • Meryl Skinlife fibers
  • High-density woven arch band
  • Flat toe seam
  • Open mesh cuff panel
  • Antimicrobial
  • Breathable and moisture wicking

Tech Specs

Meryl Skinlife
Recommended Use:
Manufacturer Warranty:
30 days

Size chart



Castelli Socks
US Men's shoe
4-7 8-10 11-14
US Women's shoe
5-7 8-10 11-12
How to Measure:
For best results, take measurements over your underwear.

Community & Reviews

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Castelli Free 9 Sock

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Here's what others have to say...

5 5

The best summer socks!

  • Familiarity: I've put it through the wringer

I have four pair of these socks. They are the best summer socks I have owned. I have tried socks from companies like Rapha, Swiftwick, and Defeet, and these are the best. They fit like a good cycling sock should. They don't bunch up and they are not too loose. If you have a nice pair of cycling shoes, I highly recommend getting a good pair of socks so your shoes will fit like they should. I wear a size 45 in Sidi and the L/XL fits perfectly.

Avg. ride time: 7h 8m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.
5 5

Great lightweight sock

  • Gender: Female
  • Familiarity: I've put it through the wringer

I am a women's 9 and I bought a L/XL, though I was weary of the size since a women's 9 is usually a men's 7. Originally this footbed on the sock was way too long, but now fits perfectly after one machine-wash on delicate (had only handwashed before). The band can be rather snug and the logo stretched if you have bigger legs but the sock won't fall down! Great fluoro color, no bunching, and very breathable.

Avg. ride time: 7h 28m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.
5 5

Nice socks

  • Familiarity: I've put it through the wringer

These have been great so far this summer. I wear a 9-9.5 size shoe and ordered the L/XL size for these socks. I would go with the smaller size if I order more - the foot area of the sock is just a little too long for my preference (not the height of the sock, the foot area).

5 5

The best summer cycling socks!

  • Familiarity: I've put it through the wringer

Castelli Free 9's are my absolute favorite summer cycling socks. These socks are amazingly well ventilated on the top of the foot and all the way around to the top of the cuff. You can use these socks on even the hottest Summer days.

And 9 cm is the -perfect- height. You see this cuff height the most in the pro peloton. It covers the ankle and the achilles tendon, but does not extend onto the calf muscle.

In sum, these Casteli socks provide great quality, fit, ventilation, and they stay up. Lastly, they look -awesome- if you wear white cycling shoes!

Sizing: I'm a 45.5 euro in Sidi (10.5/11.0 USA). I bought both the L/XL and the XXL. The XXL fit better. If your foot is 46 euro or larger, definitely go with the XXL. Made in Italy.

5 5

These socks though!!!

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

Yeah, just buy a pair or two, or 5 like I did.
Fit great, look great ride well.