Edelbrock part #8729 spacer kit includes a 7/16" thick spacer and two .045" thick gaskets for a total thickness of 1/2". The kit also has new base to upper fasteners to accommodate the spacer. There are several benefits to the kit. First it raises the upper manifold 1/2" for increase valve cover to upper plenum clearance. This is needed to run a taller cover such as when roller rockers are used. It also provides heat insulation between the lower and upper manifolds. As a third benefit the 1/2" extra runner length helps to produce more torque. Fits all Performer RPM II 5.0 PN 7123 based manifolds.