I have a few drain plugs that are 1/2npt stainless. Now I ordered a spare drain plug and the one I got was advertised as a replacement. The sizes are almost identical, but the new one will only go in a few threads. Im sure they are different sizes.
Are there different sizes for drains? Or did I possibly get one that didn't get sized right?

This is what my drain looks like


Thanks!

you could go to ace hardware and pick up a 1/2" brass pipe thread plug and see if it fits better. Pipe threads are a not very exact science, it's more of a mix and match to get what you want especially when they are plated.

I have one that looks like the op's. Is stainless also.

Mine does not have pipe thread, as the plug is o-ringed.

Wonder if that is what you are running into ? Trying to put a pipe thread in a regular thread ?

Okay, just enlarged your pic - I see an o-ring under the plug.

I have a 1/2 stailess pipe plug with a SS wingnut welded to it.
Works great NO WRENCH NEEDED
My FORMULA 292 has 3 plugs