Stolen bottom bracket axle kitthe stolen usmid bottom bracketkit is supplied with a mid size bearing housed within a us size shell thefore offering a great value option for bmx bikes using either size frame shell this kit uses 2 japanese sealed bearings that will accept any sealed 19mm crank axle another great featureof the us size cups isthe factmost complete bmx bikes using this shell onlycome supplied with alooseball bottom bracket and 1 piece style cranks using this kit the user