This casual sock is designed with soft, skin-friendly cotton, making them a wardrobe essential! With comfort and durability in mind, these socks couple perfectly with your favorite pair of Birkenstocks! FEATURES Learn more about the features Elasticated Pressure-Free Cuff94% Cotton 4% Polyamide 2% Spandex (Lycra) PRODUCT DETAILS Details for the Birkenstock Cotton Slub Sock Women's - Blue White Sock Style: Mid-Calf Sock  Fit: Stand with your heel flush against a wall and place a measuring tape underneath your foot. Read the measured foot length in millimeters from the back of your heel to the front of your longest toe.If you are between two sizes, choose the next highest size for a comfortable fit. Size 36-38 Women's:  36EU 5-5.5US 3,5UK 230mm 37EU 6-6.5US 4,5UK 240mm 38EU 7-7.5US 5UK 245mm Size 39-41 Women's : 39EU 8-8.5US 5,5UK 250mm 40EU 9-9.5US 7UK 260mm 41EU 10-10.5US 7,5UK 265mm