So I'm changing the oil on an RV onboard generator (Onan QD3200) and I come across the oil drain plug. Normally I always replace these with magnetic plugs, but as I'm servicing it I come across this: In all my years I've never seen a two-piece oil drain plug like this; it's a cap that unscrews, and the center is a separate piece that drops out and apparently maintains it's seal to the outer cap using an o-ring inside the cap. Can anybody tell me what standard this is / who makes it / is it common? Been looking all over and I can't find any info. I understand it's an extension piece for the original drain, but I'd still like to get a replacement magnetic cap for it if possible. Thanks in advance for any help.