Shimano acera m391 square tapershimanos acera m391 square taper 9 speed chainset is lightweight and durable and is equipped with shimanos hyperdrive sg x chainrings which provide quiet and trouble free shifting features material aluminium crank arms with steel chainrings tooth count223244t bottom bracket typesquare taper jis chainring bcd10464 bolt pattern4 bolt hyperdrive sg x chainrings crank fd typemountain triple chain compatibility9 speed pedal spindle916 crank inten