This is the Connecting Rod for the OS Engines GT55 Gasoline Airplane Engine (OSMG1555) This part connects the crankshaft to the piston. FEATURES: Machined aluminum Pre-installed roller bearings INCLUDES: One Connecting Rod - part #7 in engine part list REQUIRES: Assembly into engine SPECS: Length: 94mm (3.71") Top bushing diameter: 9.5mm (.37") Bottom bushing diameter: 13mm (.51") lmm 04.13.10 ir/jxs