what is the difference between fitbit alta small and large?
The Fitbit Alta HR comes in three band sizes: Small, Large, and X Large. To figure out the size band that would properly fit your wrist, check out our guide to measuring your wrist for a Fitbit. ... Basically, Small fits 5.5"-6.7" (140mm-170mm) wrists. Large will fit those who are 6.7"-8.1" (170mm-206mm).