Get the perfect Apple Watch Series 9 by choosing the best strap for your wrist. For maximum comfort, Apple designed Sport Band in two sizes. For the 41mm case, S/M will fit 130 - 180mm wrists and M/L will fit 150 - 200mm. For the 45mm case, S/M will fit 140 - 190mm wrists and M/L will fit 160 - 210mm. Alternatively, go for Sport Loop. When choosing the 41mm case, the one size strap will fit wrists 130 - 200mm. When choosing the 45mm case, the strap will fit 145 - 220mm wrists. The Stainless Steel case comes with the Milanese Loop. Choose the 41mm case for a strap that fits 130 - 180mm wrists, or the 45mm case for a strap that fits 150 - 200mm wrists.