A traditional rugby union kit consists of a collared jersey (often imitated by fashion labels and called a "rugby shirt"), shorts, jockstrap / compression shorts, long rugby socks and boots with studs. Some modest padding is allowed on the head, shoulders and collarbone, but it must be sufficiently light, thin and compressible to meet IRB standards. Most players also opt to wear a mouthguard to guard against concussion and chipping of the teeth.