LFR5201-10KDD 12mm ID x 10mm U-Groove Track Roller BearingLFR5201 10KDD U Groove Track Roller Bearing 12mm ID x 35mm OD x 15. 9mm Width U Groove Guide Roller The LFR5201 10KDD is a U groove track roller bearing designed for use in linear motion systems, guide rails, and track rollers where quiet, smooth, and durable tracking is essential. Item: LFR5201 10KDD Bearing Type: U Groove Track Roller Bearing Quantity: One Bearing Inner Diameter (dw): 12mm Outer Diameter (D): 35. 0mm Width (C B): 15. 9mm Groove