Soft, breathable and lightweight, the Sport Loop features a hook-and-loop fastener for quick and easy adjustment. The double-layer nylon weave has dense loops on the skin side that provide soft cushioning while allowing moisture to escape. On the reverse side, the attachment loops are securely anchored for superior durability. 41mm: Strap fits 130–200mm wrists. 45mm: Strap fits 145–220mm wrists. Works with all versions of Apple Watch. Material: Woven Nylon