一種圓柱形裝置,包含三個或更多個長方形球迴路,並配有一個保持器以引導球沿正確的路徑移動,專門設計用於滑動直線運動軸,以最大限度地減少摩擦和磨損。
0.6246 inches minimum and 0.6250 inches maximum overall outside diameter, 0.8600 inches minimum and 0.8750 inches maximum overall length, 0.6240 inches minimum and 0.6400 inches maximum distance between retaining rings, instrument series style designator