Unfortunately, the EZ Oil Drain Valve cannot be fitted to some models of Holden Commodore without modification or "hack".
The pictures below are of the sump plug on a VY 3.8L V6 engine. As you can see, there is a "lip" on the top edge of the drain hole. This lip sits within the diameter of the valve, so the valve hits this lip before the valve can seat properly.
We currently do not offer an extension/adaptor for this valve, so the only possible solutions are to grind down the lip so the valve can seat or to use a thick alumimium washer to space out the valve to clear the lip. We have not tried either hack.
The valve that is the same thread as the sump plug is EZ-8 (24mm x 1.5). It's diameter is 38mm. The effective diameter of the lip is 34.3mm, so about 2mm (3.7mm / 2) has to be ground back.
Thanks to Aaron for the pictures.