Description The Robert Axle Spacer Kit RAP036 is designed for use with 12mm thru axles. These spacers allow Robert Axle’s wide range of thru axles to fit less common bike frames. The internal diameter is for 12mm and the outer diameter is 19.9mm, to match the diameter of the axle head. The spacers are designated by their thickness. They are all the same diameter. Designed, machined and tested in the USA. RAP036 Spacer Kit includes: 1x 3mm Flat Spacer 2x 6mm Flat Spacer 1x 6mm Tapered Spacer