The Apple Watch Sport Band is made from a flexible rubber material called fluoroelastomer with a metal pin closure. 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.
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 Nike Sport Band differs from the Apple Sport Band in that the Nike version uses a perforated design to make it slightly lighter and more ventilated. This Pride Edition design is primarily white, and each perforation uses colors from the LGBTQ flag. The Pride version package states that “Apple and Nike are proud to financially support LGBTQ advocacy organizations working to bring about positive change.”
The Apple Watch Sport band has been available in the most colors so far. As of December 2021, 110 Apple Sport Band colors were available with an additional 36 Nike Sport Band colors (according to the Bandbreite app).
This example comes with S/M and M/L sizes for the 44 mm Apple Watch that is also compatible with 42 mm and 45 mm sizes.
Sources: Apple, Bandbreite app