Whether it's a chilly winter morning or bluebird spring afternoon, it's always easier to get after one more lap when you're comfortable. PhD Nordic socks were designed with that long-distance comfort in mind, from mesh zones for ventilation to strategic cushioning in the toe and heel that provides extra padding without sacrificing boot fit. We've added Indestructawool Technology in high impact zones to increase durability, without the bulk. You'll also get a secure fit above and below the heel, under the arch and across the instep thanks to the 4 Degree Elite fit system. So keep on moving, because we've got comfort covered.