I saw a P229 slide that is sold separately. I think it's the one sold on their site. It's got some numbers etched on the side. Its got the Romeo Pro 1 mounted already.
Question - is a 9mm or a 40/357 slide??

If you are referring to this one:
https://www.sigsauer.com/rx-sl...-p229-romeo1pro.html
or this one:
https://www.sigsauer.com/rx-sl...-p229-romeo1pro.html

Both indicate in the description.

quote:

*Please Note*
This slide is for 9mm barrels only and is not compatible with .40, .357 SIG.