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Item # CST2610

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Item # CST2610

Sock it to 'em.

The Castelli Free 9 Sock is to regular socks as space shuttles are to balsa-wood gliders—the basic design is similar, but everything that matters is totally different. The Free 9 is woven from Meryl Skinlife fibers, which are engineered to be antimicrobial, highly breathable, and moisture wicking, so your feet stay fresh, dry, and comfortable. A high-density woven band under the arch supports your foot and prevents slippage without adding any extra thickness, a flat toe seam prevents irritation, and an open mesh panel at the cuff increases airflow to provide unbeatable ventilation.

  • 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:
1 year

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.

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Great socks

  • Familiarity: I've used it several times
  • Fit: True to size

My new favorite socks. The L/XL fit my 10.5 feet perfectly. Fabric feels soft to the skin. They are light and airy - perfect for summer or any non-cold day. They look very sharp too!

Updated for 2016

    Castelli has updated the color scheme slightly on the white/blk for 2016. The top of the band is now all black (not mostly white as before). Functionally, the socks remain the same. These are GREAT summer road socks!

    Sizing: I wear a 45 Shimano road shoe. I like the fit of the XXL best.

    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: 6m per week
    • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

    Great lightweight sock

    • 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: 9h 9m per week
    • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

    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).

    The best summer cycling socks. Period.

    • Familiarity: I've put it through the wringer

    Castelli Free 9's are GREAT 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.

    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 socks provide great quality, fit, ventilation, they stay up, and they look awesome. And made in Italy.

    Sizing: The official sizing chart at the Castelli website is correct.

    Cycling shoe size: 36-39 = S/M
    Cycling shoe size: 40-43 = L/XL
    Cycling shoe size: 44-47 = 2XL