Here is the data from the chart on the package to assist those of you thinking about buying these:

Based on Forearm 'circumference'

Youth = 7" to 8"
Small = 8" to 9"
Medium = 9" to 10"
Large = 11" to 12"

Note that the measurement starts 2 inches from your elbow tip. Find that spot and measure 'around' your arm.

Also, the material at the top that says Shock Doctor on it is really at least an inch wider than it appears in this picture. Not a big deal if you don't mind folding it over, or don't mind it enclosing your elbow.

I ordered the large and they fit a little tight, but I expect that because I lift and my arms are a little bigger than the large size. Pretty cool looking and they offer good padding where you need it.