TRB RC 10pcs 15x21x4mm Precision High Speed Ball Bearing, Chrome Steel 52100 (GCr15) ABEC 3 with Blue Rubber Seals. Chrome Steel 52100 (GCr15) ABEC 3 Races Hard Chrome Steel 52100 (GCr15) BallsRubber Seals to Help Fight Dirt Great Quality & Value For Applications Dimensions as follows: ID, OD, Width: 15x21x4mm Bearing is Compatible with Part #: Axial: AXA1243Arrma: AR610018Losi: LOSA6944Mugen: E0601Team Associated: 89162 TRB RC M15x18mm Dia. Steel Shim Pack 10ea 0.1, 0.2, 0.3, 0.5mm Width / Thickness. Dimensions and Qty's: ID = 15mm OD = 18mm Width/Thickness = 10ea 0.1mm 10ea 0.2mm 10ea 0.3mm 10ea 0.5mm