These pressure socks help to prevent swollen legs or ankles, deep thrombosis of the vein (DVT) and stimulate the blood circulation during a long travel. Clinical tested and approved, (comply with BS 7563:1999). The pressure socks do not offer guaranteed protection against medical problems. Size: S 35-38 M 39-42 L 43-46 Weight: 53g/59g/65g Fabric: 95% polyamide (nylon) and 5% spandex.