All TTS sleeves are designed to be modular so you can wear them in a variety of ways. Simply measure around the area of the arm or leg you'd like to cool and look for the right size below.
If you don't have a soft measuring tape, simply use a piece of string to find the circumference and use a measuring stick, a ruler, or a rigid measuring tape to find the length.
Suggestion, use the size charts as they are listed. In other words, use the Brachial TTS sleeves for the bicep and the knee. Use the Radial TTS sleeves for the wrist and ankle. Use the Dual TTS sleeves for your arms.