Shimano Altus M311 Crankset w/ Guard The Shimano Altus line is Shimano's budget friendly mountain groupset, bringing time-tested Shimano quality to the entry-level cyclist. The Altus M311 Crankset is an excellent replacement crank for entry-level bikes and includes a built in chainguard to keep pants and shoelaces out of the drivetrain and grease and grime off of your clothing. Specifications Bottom Bracket Not Included Arm Length: 170mm, 175mm Spindle Interface Type: Square Taper JIS Spindle Length: 123.0 mm Chainring BCD: Riveted Crank-FD Type: Mountain Triple Chain Compatibility: 3/32" Pedal Spindle: 9/16" | Shimano Altus Fc-M311 Crankset W/Guard Black, 175mm, 22X32X42T