Chris King bottom bracket Fit Kits are used with Chris King bottom brackets to ensure that cranks mate perfectly with bearings, extend product life, and reduce the potential for noise. Fit Kits will also allow you to use one bottom bracket with a wide array of cranks, if you happen to change you cranks in the future.Fit Kit 2 DUB B is for DUB road cranks with ThreadFit 30 bottom bracketsFit Kits extend the useful life of both your bottom bracket and your cranks, it reduces the potential for noise, and it also allows you to use one bottom bracket with a wide array of cranks Chris King Bottom Bracket Fit Kits Cup Conversion Kit UPC: 841529096248