Mongoose Vinson Fat Tire Bike Mongoose aluminum fat bike frame and rigid fork are sturdy and durable for a rugged riding experience 24-Speed SRAM X4 trigger shifters, a Shimano front derailleur and SRAM X4 rear derailleur means smooth shifting and a wide, versatile gear range Dual mechanical disc brakes supply crisp all-condition stopping. Rims : Aluminum 100mm w/35mm Holes Knobby 4 inch wide fat tires can handle everything from Sandy paths to snowy trails, while light and strong alloy rims add strength and durability Durable 3-piece alloy crank keeps gearing smooth and reduces pesky maintenance on your end