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Item # CST003F

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  • Black, S/M ($16.95)
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Item # CST003F

Proven in labs and stuff.

Extensive clinical study and mounting evidence in various fields of research has lead scientists around the industry to conclude that Merino wool is freakin' rad. It's naturally antimicrobial, extremely breathable, yet it one of the warmest fabrics per weight you can buy. Especially when ribbed around the ankle and reinforced to support of the midfoot arch, it makes a fantastic cool-to-cold weather cycling sock, and that's exactly what the Castelli Merino Socks are.

Tech Specs

100% Merino wool
9 cm
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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These reviews raving on SOCKS cracked me

  • Familiarity: I've put it through the wringer
  • Fit: True to size
  • Size Bought: L/Xl (45 shoe)

up until I got a pair last year. They are pretty much the best socks ever. I got 4 more pair because I wind up using them off the bike as much as on. I live in Florida so they are a bit much 6-8 months out of the year but you won't be disappointed if you are looking for a thicker, well made sock for chillier days.

favorite socks

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

awesome fit, perfect length, nice cushion on the sole but not too much...i'm always hunting for better socks and these are hard to beat.

Avg. ride time: 0m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

Best Socks I've Used

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

So far these are the best socks I've used. They're extremely comfy to wear, but they are quite thick so if your shoes are to tight as they are, you might want to opt for a thinner pair, so far I've had no problems. Surprisingly I've worn them up to 75F before they've gotten uncomfortably hot.

I got Large, and I currently wear a 10-10.5

Best Socks I've Used
Unanswered Question

I've read several reviews on BC's sister web site - Competitive Cyclist - that indicate the white socks aren't pure white as shown. Rather, they're described as "off-white" or "cream." Can someone from BC or who owns these weigh in? Thanks.


  • Familiarity: I've used it several times

Castelli Merino wool socks made in Italy for $17? Are you kidding me?!?

These Castelli socks are a work of art. The quality is 10/10. These are a steal at this price.

Wool offers the best wicking material and zero odor (naturally). Wool is a superfabric! So, these socks are super comfy and breathe fantastically and stay dry. Very versatile. Perfect for 45°-70° weather.

Sizing: I wear a 45.5 shoe in Sidi (10.5-11.0 USA). The L/XL just fit but the XXL fit better. Wool socks do shrink slightly. If you wear a 45+ shoe, definitely buy the XXL.

very nice socks

  • Familiarity: I've used it once or twice and have initial impressions
  • Fit: True to size
  • Size Bought: xxl - size 11 foot

I ordered one pair of all of the Castelli socks. I returned all of the others as they more closely resembled tube socks. These socks have a nice angle that anotomically fits the angle from foot to leg and doesn't crease in that area when the foot dorsi flexes. The wool is soft and stretchy. Too bad the others aren't made like this pair.