one piece axle

The crankset (in the US) or chainset (in the UK) is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain or belt, which in turn drives the rear wheel. It consists of one or more sprockets, also called chainrings
or chainwheels, attached to the cranks, also called arms or crankarms, to which the pedals attach. It is connected to the rider by the pedals, to the bicycle frame by the bottom bracket, and to the rear sprocket, cassette, or freewheel via the chain.

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