Caliper Bridge Spacer Kits contain bolts, bridge spacer and other hardware to convert Narrow Dynalite, Narrow Dynapro and Forged Narrow Dynalite Calipers to different rotor widths. 300-6588 will convert 0.38 and 0.81 to 1.25" wide rotor width, 300-6589 to will convert spacing to 0.81"