SHIMANO SLX M7000 Mountain Bicycle Crank Arm Set - FC-M7000-11-1 Balance of strength and lightweight by 2pcs crank construction Improved driving rigidity Close ratio gear combination for minimum shifting gap and maintaining rhythm (FC-M7000-11-2) Enhanced chain retention (FC-M7000-11-1) Better sealing and better rotation Small ball bottom bracket. NO CHAINRING