Pit Bike Swing Arm Bearings With most of the main stream manufacturers buying in their swinging arms form the same suppliers; the most common bearing fitted to a swing arm are these. Available in sizes fitting most bikes from M2R, Demon X, WPB, Stomp, Evo etc etc. Simply select the correct bearing code for your bike in the drop down menu. Summary: Most common size used Fits all M2R models, except KX90F Fits most other mainstream manufacturers