Made from a custom high-performance fluoroelastomer, the Sport Band is durable and strong, yet surprisingly soft The smooth, dense material drapes elegantly across your wrist and feels comfortable next to your skin An innovative pin-and-tuck closure ensures a clean fit What's in the Box: Apple Watch Sport Band (includes straps that can be configured for either S/M or M/L length), Regular Sport Band (comes with S/M & M/L pieces) You can match most straps with any Apple Watch Series 3 or newer case of the same size. The 41mm straps work with 38mm and 40mm cases; the 45mm straps work with 42mm and 44mm cases.