7075-T6 aluminum alloy CNC cutting and forming 7075-T6 aluminum alloy screw lock plate Cr-Moly 16T adjustment gear plate can rotate the ten-speed flywheel 11/13/15/17/19/21/24/28/32/36 For 11/13/16/19/21/24/28/32/36/40T or 11/13/16/19/21/24/28/32/36/42T - the front chain link needs to be converted to a single piece - (1)