Shimano Altus FC-M315 Square Taper 7/8sp

Entry level 7/8-speed double chainset offering slick hyperdrive shifting performance for off road enthusiasts
Hyperdrive SG-X chainrings for fast and smooth gear shifts
7/8-speed compatible steel chainrings
For use with 123 mm square taper bottom brackets
With a 51.8 mm (boost) chainline for use in conjunction with 148 mm O.L.D.