In petroleum and natural gas extraction, a Christmas tree, or "tree", (not "wellhead" as sometimes incorrectly referred to) is an assembly of valves, spools, and fittings used for an oil well, gas well, water injection well, water An assembly of valves, spools, pressure gauges and chokes fitted to the wellhead of a completed well to control production. Christmas trees are available in a wide range of sizes and configurations, such as low- or high-pressure capacity and single- or multiple-completion capacity. See: choke, frac stack, frac tree, pressure gauge, production tree. A Christmas tree is an assembly of valves, spools and fittings used for oil, gas, water injection, water disposal, gas injection, condensate and other types of wells. It is named for its resemblance to a decorated tree at Christmas.