This is a device used on a drilling rig to actually rotate the drill pipe in order to drill the well. This device is complicated and expensive. It hangs in the derrick and is operated by the driller on the rig floor. It is used to speed up the drilling process versus using a conventional rotary table to rotate the drill pipe and bit. The top-drive is used primarily offshore due to the potential to save money by drilling faster as the overall costs offshore are usually 5x to 20x more expensive than onshore. The top-drive is used to drill complex directional wells and horizontal wells due the ability of the top-drive to be manipulated accurately with respect to drilling directionally. The top drive replaces a rotary table as the means to rotate the drill pipe and bit. The rotary table is a relatively inefficient mechanical method used to rotate the drill pipe. However, it is cheaper and on a normal drilling operation, the rotary table works cost effectively. Top-drives are made by Tesco, NationalOilwellVarco, and CanRig.