Hybrid Ceramic RM2-2RS 3/8" Si3N4 V-Groove Guide Bearing W2-2RSRM2 2RS Ceramic V Groove Guide Bearing 3 8" ID Sealed with Si3N4 Ceramic Balls The RM2 2RS ceramic V groove bearing features silicon nitride (Si3N4) balls for ultra smooth motion, low friction, and high wear resistance. With a 3 8" inner diameter and sealed design, its perfect for precision track systems in demanding environments. Inner diameter (d): 3 8" (9. 525mm) Outer diameter (D): 30. 73mm V groove width (A): 18. 24mm Bearing width (C): 11. 1mm