Human beings come in all sizes and shapes, but wrist sizes vary less than you might expect and are correlated more to height (frame size) than muscularity. Taller people tend to have larger wrists. The average wrist size for all adults is 7.17 inches. Size "Medium" is based on DADmo's wrist, and DADmo is as average as they come.
Approximate Finished Lengths:
This may or may not be helpful. The length of each model varies somewhat according to the thickness and stiffness of the cord to achieve the proper fit.
Single-Wrap Cords: Small (19cm) / Medium (21.5cm) / Large (22.5cm)
Double-Wrap Cords: Small (39.5cm) / Medium (43.5cm) / Large (45.5cm)
Triple-Wrap Cords: Small (21.5cm) / Medium (24cm) / Large (26cm
Regular fits waist/hips up to 36"
Long fits waist/hips up to 42"
Trim to Fit: Webbing can also be cut and very carefully re-sealed with a lighted match or candle.