Ultimate Performance Ultimate Compression Elastic Knee Support (small) The compressive element also stimulates blood flow which can help prevent the build up of lactic acid during and post activity. This reduces the prospect of cramp and stiff ness whilst also being a valuable recovery and rehabilitation tool to injury. Features: The compressive element also stimulates blood flow which can help prevent the build up of lactic acid during and post activity. This reduces the prospect of cramp and stiffness whilst also being a valuable recovery and rehabilitation tool to injury.SIZING - measure around the centre of the kneeSMALL 12-14" (30-35cm)MEDIUM 14-16" (35-40cm)LARGE 16-18" (40-45cm)XL 18-20" (45-50cm) Specifications: Dimensions: H:20.1 x W:13.8 x D:4.7 cm Model Number: UP5150S