These great wading socks go inside your wading boots when fishing, to help keep feet dry and comfortable. USED ONCE in a Colorado River before discovering don’t like fly fishing! See size guide below. Unisex. Medium fits Womens 10-11 & Men’s 8-9. ** “With a low-profile design and contoured anatomical fit, Simms Neoprene Wading Socks keep active feet comfy and debris-free when wet wading. Constructed using 2.5mm abrasion-resistant neoprene in the upper, and perforated 2.5mm neoprene underfoot for drainage Anatomically correct left and right patterning for superb fit and easy don/doff Unisex sizing: XS (M's 4-5, W's 6-7) S (M's 6-7, W's 8-9) M (M's 8-9, W's 10-11) L (M's 10-11, W's 12-13) XL (M's 12+) FABRIC TECH: 2.5mm neoprene”