This is the Replacement Rear Bearing for the OS 18TM Engine. / This bearing supports the rear of the crankshaft. / / FEATURES: Open race design / / INCLUDES: One rear bearing / / REQUIRES: Installation into engine. / / SPECS: Inner Diameter: 12mm / Outer Diameter: 21mm / Thickness: 5mm / / cmc 02/16/05 / ir/jxs