Custom bearings and high performance seals in all e*thirteen bottom brackets deliver supreme durability and smooth spinning. Available for cranks with either 30mm spindle (Race and Plus cranks) or 24mm spindle (Base cranks). Available for frames with 68mm, 73mm, 83mm and 100mm threaded BB shells. Gravel BB fits 68mm BSA shells with no spacers for road fit.Note regarding T47 Bottom Brackets: The T47 BB we offer is an EXTERNAL cup version and is not compatible with the T47 Internal "standard." 100mm BSA needs can be met by purchasing either the 73mm or 83mm BSA BB and installing the cups without the centertube or reusing the existing centertube if you are already running an e*thirteen BSA BB. All Bottom Brackets include our 1 year, no questions asked guarantee.