COPPER FIT KNEE: This specially-designed knee compression sleeve features a high-density, activated copper infused into the yarn. It provides comfortable support to help ease soreness, stiffness and pain. And, it also helps enhance circulation, and reduces muscle strain & fatigue. Great for men and women. Polyester/spandex infused with copper ions for antimicrobial protection. For proper fit, measure the circumference of your thigh 5" above the center of the knee. Specify thigh circumference when ordering: M (15 1/2"-17"), L (17 1/2"-19"), XL (19 1/2"-21"). (For Copper Fit Elbow, see item 26686 - Sold separately).