The designation "One Size" on the Fitbit Versa 2 (40 mm, aluminium) means that the device is equipped with interchangeable wristbands that are available in different sizes. This makes it possible to adjust the wristband to the individual wrist size.

- The device itself has a fixed size of 40 mm, but it comes with small and large wristbands that can be customised separately.
- The compatible wristbands are available in different colours and materials and can be interchanged to ensure the best possible fit.