Some generation 1 & 2 engines, up to serial no. 3596, may require fitting this Distributor Cap Shim P/N: 4A984A0D. MTD-05-2024 should be consulted. Fitting of the 2mm shims where not required may have a detrimental effect. 2nd photo shows the shim with distributor cap (not included). Skycraft only sell genuine Jabiru supplied parts. Beware of inferior pattern parts.