Enables a Holden caliper to be spaced to take a wider disc rotor.

On HT, 1969 to 1970 models, the V8 takes a wider rotor (RDA3) than the 6 cylinder (RDA2). These spacers were original on this model but can be fitted to the six cylinder calipers so the wider rotors (RDA3) can be fitted.
Also standard on all HG 1971 to 1972 with disc brakes.

The same applies to-:
LC Torana GTR XU1 1969, 1970, 1971, 1972.
LJ Torana GTR XU1 1972, 1973, 1974. (RDA4 = 16mm Thickness)