Compression garments are pieces of clothing that fit tightly around the skin. In medical contexts, compression garments provide support for people who have to stand for long periods or have poor circulation. These come in varying degrees of compression, and higher degree compression sleeves, such as sleeves that provide compression of 20–30 mmHg (2.7–4.0 kPa) or higher, typically require a doctor's prescription. Compression garments worn on the legs can help prevent deep vein thrombosis and reduce swelling, especially while traveling.