Besjex Compression Upper Arm Sleeve (1 Pair) for Comfort and High Performance in Sports - for Men and Women - Great for Cycling, Running, Basketball, Baseball, Football, Golf Size Guide: Small 10"-11" / Medium 11"-12" / Large 12"-13.5"/ XL 13.5-15.5 How to measure: Measure the largest circumference/girt of your upper arm, or bicep. Compression fabric reduces soreness, cramping and fatigue Anatomically-designed for additional elbow support to help reduce fatigue and elbow soreness Improves circulation for better muscle recovery; Stay fresh and loose for elite performance and increased stamina late in the game