How are they on the plug when you remove them from the box? I never noticed a different diameter either but I'd assume they way they were put on at the factory is the way they need to be installed. Anyway that's the way I've always done it & never had an issue arise.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.