A traction elevator is the most common type of electric elevator, in which the car is raised and lowered by steel wire ropes or flat belts that pass over a drive sheave connected to an electric motor. The drive unit can be geared or gearless, and the system is balanced by a counterweight. Traction elevators are suitable for virtually all building types and heights, offer high energy efficiency (especially with regenerative drives), and are available as conventional (with machine room) or MRL (machine room less) configurations.