Associated head shim set is constructed of aluminum (Head Button) and brass construction (Head Shims). This is also called the Head Button and goes between the cylinder head and the crankcase. The glow plug screws into this part.
Diameter: 1.383" (35.15mm) (Head Button)
Diameter: 1.000" (25.45mm) (Outside of Shim)
Diameter: 0.712" (18.08mm) (Inside of Shim)