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. You can match these straps with any Apple Watch Series 4 case of the same size. They also work with all previous versions of Apple Watch, including Apple Watch Series 3. Physical specificationW40, . FeaturesAccessories included: Apple Watch Sport Loop strap.