Do Wristbands come in different sizes?

Yes they do!

SPORTS EDITION
Pavlok Sports comes in Pearl White or Obsidian Black with a one-size-fits-all silicon wrist band.

https://pavlok.com/pavlok-3-pro-buy/

DELUXE EDITION
Pavlok Deluxe comes in Obsidian Black, Rose Gold or Aegean Silver with a Metallic Mesh Magnetic wristband.
Deluxe also comes in two sizes:
Small for wrists from from 5.31” (13.5 cm) to 6.18” (15.7 cm) in circumference.
Regular for wrists from 5.98” (15.2 cm) to 7.20” (18.3 cm) in circumference.
https://pavlok.com/pavlok-3-pro-buy/