CastelliGregge 12 Sock

Merino—comfort for all conditions.

Full-length coverage and the versatility of Merino wool make the Castelli Gregge 12 Sock a great addition to your early- and late-season gear.

  • Reviews
  • Q & A


  • Fit: True to size

Top of the line. Majority of my gear is Castelli. These are great socks. I will wear these in colder riding weather, definitely not summer socks for me.


  • Familiarity: I've put it through the wringer

Castelli is iconic in the cycling world. Made in Italy, these socks are a work of art. The quality is 10 out of 10.

I own several pairs of Gregge 12 and Castelli Quindici (15) wool socks. Love them both. The only difference is that the Gregge feature a 12 cm tall cuff and the Quindici are just slightly taller at 15 cm. And of course the color schemes are different. Castelli officially rates them both for use in 23-60° F weather.

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

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

I wear a 45 in Shimano. The 2XL fit perfect -especially after a few washings (wool does shrink a little). If you wear a size 45+ cycling shoe, definitely buy the 2XL.


  • Fit: True to size

Does perfectly what you want merino socks to do.


Castelli socks

  • Fit: True to size
  • Size Bought: Large

The older I get the more comfort and performance of clothes matters to me. Castelli kit such as jerseys, jackets, gloves, shorts isn't top drawer IMO perhaps because it's outsourced to Asia, but I do think the socks (made in italy) are undeniably great. I love Exteondo kit for just about everything they make with the exception of socks where I believe Castelli is superior.

These particular socks are very comfortable. They aren't the warmest Castellis I've used but they are good for riding in 40 degree weather in the northwest and I just used them on a 65 degree ride in the Santa Cruz Mountains with no overheating issues.

Castelli builds great quality into this product and it should last many rides and wash cycles. I give them a big "thumbs up".

I'm a 10 sneaker size; 45 Sidi size and the Large socks fit just about perfect for me.


    Very comfortable and quite thick, which is great considering how stiff cycling shoes can be.

    Great merino socks

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

    These are wonderfully warm merino socks. Have used them for winter riding for a couple of months now and they have become my favorite. My perception is that the Gregge socks are warmer than my pair of Castelli's Quindici socks.

    Maybe my favorit winter sock

    • Familiarity: I've put it through the wringer
    • Size Bought: L/xl - i wear size 42.5 shoe

    Well made, looks good and fits well once u figure out the size you need. Castille is always good stuff imho.

    So warm, I never want to take them off.

    • Familiarity: I've put it through the wringer

    The band around lower calf holds great but not too tight to give you discomfort at the end of the day.

    Two peas in a pod

    • Familiarity: I've put it through the wringer

    These socks are perfect for moderate to brisk rides (45-50 degree) and don't overheat as the day warms up. Furthermore, they hold up well and I've been wearing mine for 6 months and no issues. One tip: if you have a cycling spouse, make sure that you pick a different color pattern between the two of you.

    Warm, comfortable, pretty thick

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

    I bought these along with several other Castelli products during a Black Friday sale and have worn them a few times in in the upper 40s and low 50s combined with the Castelli Toe Thingy and have been very pleased. My initial impression was that they were really thick, and I was afraid they would make my shoes feel a bit snug. They didn't, though, and I found them to be really comfortable. My only complaint is that they're not super tall. I usually like my winter socks to go a little higher on the calf than usual, and these seem a little short. I don't necessarily expect a lot out of socks as I feel like 99% of them fit and feel the same for the most part, but these were surprisingly comfy and warm. The shorter length is the only reason I'm not giving them 5 stars.

    great sock!

    • Familiarity: I've put it through the wringer

    I loved this sock so much, I ordered a second pair. They are great for riding, have used in upper 40s with the Toe Thingy and had no issues. I also like to wear these around the house they are so comfortable!

    Nice thicker weight wool

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

    Just enough sock to keep you feet warm without booties into the 40's without overfilling my shoes. Great Style as well.


    • Familiarity: I've put it through the wringer

    These are great socks on the bike and off. Medium thickness and warm for 40 degrees and warmer. In colder temps I usually double up the socks. They are also very durable. I am on my second winter wearing them constantly. Sizing for me wearing a 45 sidi l/xl just fits and the xxl would be more comfortable. Love the stripes!

    Great in Pink for winter

      Perfect winter weight, wool sock. I get about a season or 2 out of each pair I have owned. I'm a size 12/46.5 shoe and XXL fits perfectly. Only complaint is they could be a bit taller. The pink color is my favorite. Works great for a dress sock for work too, plus it saves time when I get home from work and want to get out for a quick ride.

      Best Socks Ever

      • Familiarity: I've put it through the wringer

      I love these. Super comfy, plenty of warmth, very stylish on or off the bike. I find myself gravitating towards these for most of my non riding sock use as well. I wouldn't say that I have the prettiest feet out there, but while I'm wearing these I could be the damn Derek Zoolander of Foot Models. They're a bit too warm for the summertime, but when the temp starts dropping these are my go to footwear. Just wish they held up a bit better with all the washing.

      Great Socks for cold weather

      • Familiarity: I've put it through the wringer

      LOVE these socks--I wear them on and off the bike. The sole is extra thick making them cushy and warm. 100% wool means your feet stay warm even if they get damp/ wet. Worth the investment.

      Great Cold Weather Socks

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

      As fall sets in and temperatures fall, these are the perfect socks. They stay warm no matter what the weather is doing. They're also incredibly comfortable.


      • Familiarity: I've put it through the wringer

      I would live in these socks if I could get away with it -- they're so comfortable I catch myself wearing them around my apartment just for fun in the summer when I don't need them on rides. So cushy and warm.

      Nice Winter Sock

        These guys have been really helpful for those below 40 days, when I'm already wearing toe and shoe covers. They're nice and cushy, and even after my feet sweat they keep them warm. I've had less numb toes. They also look pretty stylish. A good sock for the money. I ended up buying 3 more pairs.

        Pretty socks

          Made in Italy. Medium heavy. Nice construction. Good ones.