The Apple Watch Sport Band was made from a flexible rubber material called fluoroelastomer with a metal pin closure. Sizes ranged from S/M, M/L, or L/XL. When purchasing an Apple Watch Sport Band, the S/M and M/L sizes are included in the box, allowing the band to fit wrists 140–210 mm. This example is the less common L/XL size.
Apple describes the Apple Watch Sport band:
“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.”
The Apple Watch Sport band has been available in the most colors so far. As of July 2022, 113 Apple Sport Band colors were available with an additional 37 Nike Sport Band colors (according to the Bandbreite app).
This example is Midnight, Apple’s current name for “black.” It includes L/XL size bands for the 45mm Apple Watch, and is also compatible with earlier larger-sized Apple Watch models.
Source: Apple, Bandbreite app