Hardtail mountain bike 29er mountain bike type mens model 2017 series specialized rockhopper frame material aluminium frame alloy 6061 aluminium bike frame sizes inch 21 19 inch bike frame sizes cm 53 44 48 56 39 cm suspension system coil suspension fork feature preload adjust gear system with derailleur number of gears 24 rear derailleur shimano alivio front derailleur shimano altus cassette sram pg 1020 rear chain wheel teeth 11 34 chain