It has a set of planetary gears with pawls engages or disengages the gears instantly. Reliable and low - maintenance.Work only with bottom bracket with ISCG 3 or 5 tabs. Crank arm 175mm. Crankset is stock part from a new single speed 29er mountain bike .Selling as a complete set include crank arms, shifter with cable, bottom bracket with sealed bearing and single speed chain. Condition 9/10. Deal at Blk 257 Pasir Ris St 21. Singapore 510257.