Let's get one thing out of the way single speeds aren't for everyone. No matter how many eggs you chug for breakfast or how many bears you leg wrestle, grinding up steep and endless climbs without the security of a granny gear isn't something that'll make everyone feel like a legend. If that sort of pain and suffering sounds like your jam, though, the Niner ONE RDO Carbon Mountain Bike Frame is your steed. Descended from the AIR 9 RDO, the ONE RDO is a light, stiff, and scorchingly fast blend of climb happy XC bike and race ready hardtail. Like all Niner frames, it was developed using the company's computer based finite element analysis, which is a fancy way of saying that the ONE's carbon layup is designed to be extra awesome. The carbon weaves, the varying tube shapes, and the frame's form are all designed to be super light and extra stiff while directing forces to the strongest parts of the bike to prevent damage. The fat CYA bottom bracket and fat 12mm thru axle direct pedaling forces into the back wheel without flexing, and the slightly curved seat stays help reduce the vibration caused by hard riding on rough and rugged trails. Unlike the AIR 9, the ONE uses Niner's oversized CYA bottom bracket interface, which fits the included BioCentric eccentric bottom bracket. It's durable, creak free, and easy to use, and if you feel like turning the ONE into a one by, you can add the necessary hardware and run any drivetrain you desire. You should also note that the ONE will only work with a 160mm brake rotor, and the rear triangle will fit tires up to 2. 35in in diameter.