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. 40mm: S/M & M/L bands fit 130–200mm wrists. 44mm: S/M & M/L bands fit 140–210 mm wrists; M/L & L/XL bands fit 160–245 mm wrists. You can match this band with any Apple Watch Series 4 case of the same size. It also works with all previous versions of Apple Watch, including Apple Watch Series 3. The 40mm band works with the 38mm case; the 44mm band works with the 42mm case.