Spinning and Grinning This rock-solid, durable performer is everything you need in a press-fit 24mm bottom bracket and nothing more. Roll on...and on...and on. Greased Lightning This 24mm BB uses quality retainer bearings sealed with waterproof grease and wiper seals for durability and worry-free cranking mile after mile. Taking A Pass On Plastic This BB uses lightweight 24mm coated steel cups that are precision CNC-machined for a solid fit and are far superior to molded plastic cups. Weather, Or Not All RF bottom brackets come with an inner plastic sleeve to keep the elements out and the appropriate spacers to ensure a perfect fit.