Tractors mainly use two kinds of brakes, mechanical and hydraulic brakes, depending upon the model and their transmission system. Under the mechanical brake category, three other kinds of tractor brakes: internal expanding shoe brake, external contracting shoe type brake, and disc type brakes are offered. The internal expanding shoe brakes are positioned inside a drum or a circular enclosure and they are often found in older tractor models. In external contracting shoe brakes, the brake shoes are positioned on the outside of a drum. They are often found in old versions of heavy-duty tractors. Disc type brakes use a rotating disc and they are used in modern tractors. Hydraulic brakes are used in larger and more modern tractors. They are best known for better braking power and control. In addition, PTO or Power Take-Off brakes are also used in tractors. These tractor brakes are used to stop PTO and ensure implements are attached safely to PTO.