I got a few of these in the mail today to keep my 509Ts protected while in storage or cleaning. I have some for my RMRs too and have found them pretty useful in keeping stuff off of lenses while cleaning when attached to handguns.
https://hugoindustries.com/products/...df626c33&_ss=r
As expected, they fit fine on my 509T that is mounted with a dedicated ADM mount, and the one I'm using as an offset dot with a Badger C1 scope mount. I don't have my slide back from Jagerwerks yet so not sure if it will fit there, but I think its likely.