Brass Cup Expansion Plug 40.08mm, Height 0.450 with Included Reservoir Cap. Dorman's Engine Expansion Plugs are available in multiple styles, including Cup Type, Pilot Seal?, Reverse Taper, Concave, Quick-Seal? Rubber and Quick-Seal ? Copper. Our uniquely designed Pilot Seal Expansion Plug ensures a leak-proof fit. We also offer Engine Expansion Plug Kits.