A fabric tube worn over the arm or leg that compresses that part of the body. This is used to provide muscle support, improve blood circulation, reduce pain, and provide warmth. They're sold in various sizes to cover different portions of the arm or leg, such as covering the elbow, forearm, entire arm, thigh, knee, shin, and entire leg. They're used in both medical treatment and sports.
Compression shorts operate in a similar manner as compression sleeves.