JJBP Front Centerlock Boost Disc Rotor Spacer Kit for mounting a 15x100 or 12x100 hub in a Boost 110 mm-spaced fork. Spacer kit includes 15 mm ID x 5 mm thick spacers for 15x100 hubs. Pair with 12 mm ID x 5 mm thick hub spacers for 12x100 forks (purchased separately). Note that this spacer requires 6-bolt rotors to be used. Requires external-style lockring tool for installation. See video for more details.