With the Caged Ball LM Guide, the use of a ball cage allows lines of evenly spaced balls to circulate. This eliminates friction between the balls, resulting in uniform alignment and motion. In addition, grease held in a space between the ball circulation path and the ball cage (grease pocket) is applied on the contact surface between each ball and the ball cage as the ball rotates, forming an oil film on the ball surface. As a result, the oil film is not easily broken.