Hardtail mountain bike 29 type mens model 2016 series serious rockaway frame material aluminium frame alloy 6061 aluminium bike frame sizes cm 40 45 50 55 cm headset vp suspension system coil suspension fork feature preload adjust gear system with derailleur number of gears 21 rear derailleur shimano altus front derailleur shimano tourney crankset prowheel front chain wheel teeth 423424 cassette shimano tourney rear chain wheel teeth 14