This is the Replacement Bearing for the OS Max RZ series engines. / This bearing will fit the following engines: / .21RZ-M / .21RZ-B / .21RZ-B(P) / .21RZ-R(P) / / FEATURES: Hardened steel bearing w/7 balls. The bearing also features a plastic / ball retainer, and a front rubber seal. / / INCLUDES: One Front Ball Bearing. / / SPECS: Outer Diameter: 19mm / Inner Diameter: 7mm / Thickness: 6mm / 11/8/96 SJM / ir/jl