Super strong, yet lightweight, Sinz Elite XXX Cranks are built specifically for BMX. When assembled, hollow-forged aluminum arms spin on smooth-as-silk sealed bottom bracket bearings and a super-stiff, hollow, 4130-chromoly, spindle. Just add your favorite Sinz 104-BCD, 4-bolt chainring and you’re ready to roll. They fit 68 or 73-millimeter bottom bracket shells.