The GX crank is an integral part of SRAMs 1x drivetrain system & features the X-SYNC 32T chainring. Each tooth’s thickness is CNC machined to work seamlessly with the chain’s inner & outer links. & with five available chainrings, you can personalise your gear range to match the way you ride. BOOST148 BOOST148 (hub width 148mm x 12mm) is targeted at 29ers & is designed to increase wheel stiffness via the hub. The hub flanges are slightly wider apart from standard hubs (142mm x 12mm) & according to SRAM & Trek "this small increase in width results in significant gains to rear wheel stiffness — comparable to a 27.5in mountain bike wheel".