The goal opening for professional ice hockey is 72" (180 cm) wide, 48" (120 cm) high, and 40" deep (100 cm). This hole is maintained stiff by a metal tube frame about 2" (5 cm) in diameter and is surrounded by a mesh net with a 1 5/8" opening (4.1 cm). The term "goalpost" comes from the fact that early goals were made out of timber. In college and university hockey, the goal height is usually between 9' and 10' (2.7 and 3 m), and the depth is usually between 18" and 20" (45 and 50 cm). Goalposts are usually made of steel or aluminum, depending on the level of competition. College hockey teams often use wood goal posts because they are cheaper than metal ones of equal strength. They are typically painted red or white when not covered by netting. In amateur hockey, the goal height is usually between 6' and 8' (1.8 and 2.4 m), and the depth is usually between 12" and 16" (30 and 40 cm). Goalposts for amateur hockey are usually made of wood, although some metal posts are used by very experienced players. They are usually painted red or white when not covered by netting.