Endo Rollers. The Line-Up Rack contains five sets of endo rollers. Each endo roller consists of two roller halves mounted on a common axle. The axle is threaded such that one complete rotation of a roller half equals 1/4" (6.35 mm) distance of movement down the axle. This allows the proper (measured) separation of wheel halves to accommodate a wide range of pipe diameters. Their universal purpose is to move, or support, the pipe lengthwise on the rack. Some endo types are spring-centered, non-elevating to simply support the pipe in its lengthwise movement. Others are powered to move the pipe. All are discussed below.

Но вот как они называются по-русски?