A very comfortable perfect fit is what you will get wit this leather look armband. Sold individually they come in sizes small, medium, and large.

Size is measurement around UNFLEXED arm just above bicep and below shoulder:

SMALL
10" to 12.5 " 25.4 cm to 31.8 cm

MEDIUM
12" to 14" 30.5 cm to 35.6 cm

LARGE
14" to 16" 35.6 cm to 40.6 cm