DeFeet Thermeator Hollow Core 6in Socks
DeFeetThermeator Hollow Core 6in Socks

Harvested from space sheep.

The Thermolite polyester at the heart of DeFeet's Thermeator Hollow Core 6-inch Socks are a synthetic version of merino wool. If extraterrestrial sheep aren't just fantasies of our winter-addled minds, they'll probably be covered in something like it. Thermolite works by creating pockets of trapped air in its hollow core yarn, which serve as extra insulation between your feet and the very real cold of winter, keeping your feet from freezing into numb clubs during those cold-weather base miles.

Thermolite is also breathable, it wicks, and it dries quickly, and the mesh instep only enhances these qualities. The gently compressive arches add support, and a touch of Lycra gives the socks an accommodating stretch.

  • Reviews
  • Q & A


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

Expectations may have been too high. I still need shoe covers under 50. Was hoping to avoid shoe covers.
A hole tore in one sock. I'd probably look else where for my next pair, but these are decent and necessary in the 50-65 degree range.

Keep Feet Toasty Sans Shoe Squeeze

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

I bought these for cold-weather rides (below 55F) because they are really warm, while staying pretty slim on your foot (read: not beefy). The problem with wearing most merino wool socks in cycling shoes is that they're usually far to thick on your foot, which compromises the shoe's fit and that makes your feet both uncomfortable and cold. Ouch!

I like that these are fairly plain socks, and since my kit is red, I ordered the black ones with the red tab on the back for a touch of fantz.

The construction seems really solid on mine so far. I own Darn Tough, Smart Wool, Swiftwick, and these seem just as solid as those.

I wear a size 13 shoe (47 cycling) and the XL is perfect.

Good warm socks

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

Good product for winter rides. I still need shoe covers under 40 but these keep me toasty up until then. Missing the last star because they show signs of wear pretty quick, like threads pulling out, but still are holding up well.