AC4® Active Comfort Sock Color:White The unique adjustable heel rest

The unique adjustable heel rest allows you to customize your stretch by increasing or decreasing the degree of stretch

PFC-free materials

Slay in Sledge

GEL™ TECHNOLOGY CUSHIONING

Complete with legendary BIRKENSTOCK design elements

AC4® Active Comfort Sock Color:White The unique adjustable heel restThe AC4 Active Comfort Sock uses two of OS1sts signature technologies for the ultimate comfort experience. The AC4 is built with nano bamboo charcoal cushion where it counts and OS1sts cooling Skin Thin Technology for temperature regulation. Made for everything from exercise to everyday, this sock features blister protection, contoured padding, and light to moderate compression for support and fit. For the best fit, it is important to use the size