Installing an XDR freehub body on a Shimano gravel hub requires a cone spanner that is 17mm in size. To begin, remove the non-drive end cap which is removable by hand. Rest the spacer on the hub’s bottom and rotate the hub's drive end cap in the anti-clock direction. Pull and twist the freehub body off, then disconnect its components. Place the ratchet, leaf spring, and a spacer in the XDR freehub body. Position the freehub body in the gravel hub shell insert then attach the amount snug with the cone spanner and use hand to fit the non-drive end cap.