Castelli Gregge 15 socks review

A low-profile merino sock to keep you warm when the weather is cool

Cycling Weekly Verdict

The low volume and thermal properties of the Castelli Gregge 15 socks make them perfect for pairing with summer shoes on cooler days. They’re cosy and comfortable to put on and remain so even on longer rides. They are a little expensive for a sock, but they do justify this by their performance.

Reasons to buy
  • +

    Warm

  • +

    Comfortable

  • +

    Low-profile

Reasons to avoid
  • -

    Merino content lower than some competitors

You can trust Cycling Weekly. Our team of experts put in hard miles testing cycling tech and will always share honest, unbiased advice to help you choose. Find out more about how we test.

The Castelli Gregge 15, with its middle-of-the-road 15cm cuff and 50 per cent merino content, is a more versatile sock, intended for a broader range of conditions and riding styles than a dedicated winter item. If it's maxed-out warmth you’re after, you’d be better off with Castelli’s Primaloft socks.

The qualities of merino wool make it ideally suited for cycling socks in colder climes. In being naturally antibacterial, your feet stand to be fresher after a ride, while the thermal properties – which remain to a surprising degree, even when wet – promise to keep your toes toasty.

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Stefan Abram
Tech features editor

After winning the 2019 National Single-Speed Cross-Country Mountain Biking Championships and claiming the plushie unicorn (true story), Stefan swapped the flat-bars for drop-bars and has never looked back. 


Since then, he’s earnt his 2ⁿᵈ cat racing licence in his first season racing as a third, completed the South Downs Double in under 20 hours and Everested in under 12.


But his favourite rides are multiday bikepacking trips, with all the huge amount of cycling tech and long days spent exploring new roads and trails - as well as histories and cultures. Most recently, he’s spent two weeks riding from Budapest into the mountains of Slovakia


Height: 177cm

Weight: 67–69kg