These simple, 5mm lightweight aluminium spacers are designed to fit onto Thru-type hub axles to enable regular 100mm spaced hubs to fit into 110mm (Boost) type spaced fork thru-axle dropouts. (1 x 5mm spacer added each side = 10mm) Please Note: These axle spacers do not change the disc brake rotor alignment position of the hub. Please consult with your dealer if you are considering these to adapt a regular Disc Brake hub to fit with a Boost system fork.  Alternative adaptor kits that include Boost Disc Rotor spacers are available for the Halo MT hub. Please see: MT Front Boost Disc Adaptor (item code: HUHAZM6FBK)