The Spacer Ball is a ball several tens of microns smaller in diameter than a load ball, inserted alternately with a load ball. Balls come into contact with each other in the load area without Spacer Balls. At this moment, the friction resistance at the contact point becomes high because the balls rotate in the opposite directions. In this case, the insertion of a Spacer Ball between the balls will reduce the friction generated by the rolling balls in the direction opposite to the load ball rotation direction and enhance operability. Note that with a decrease in the number of load balls, the dynamic and static load ratings will decrease and the rigidity will also be reduced.