This is a replacement extra strong, light weight connecting rod for the Novarossi .21 T21BF or N21B engines. This will work with any Novarossi brand engine including the Top and Rex lines. The connecting rod attaches between the crankshaft and the piston. If you are replacing the piston/sleeve in your engine, it is always a good idea to replace the connecting rod at the same time to avoid premature failure due to wear.
Note: If you are purchasing this con rod for a 21BF series engine, please consult your owners manual for correct part number.