SRAM DUB is the single replacement for 30mm and 24mm bottom bracket spindles options. They fit all frame shell standards and DUB does NOT introduce any new frame shell standards. DUB The relationship between bottom bracket spindle and bearing is the core of DUB technology. It's where stiffness meets durability. We took it a step beyond conventional thinking and made everything simpler-better integrating the relationship between chainring, crank, spindle, and bottom bracket. It's this approach to developing a complete system that equals better drivetrain performance.