If you have an older Para full size in 9x19, the RP9 mags are a very good fit.

The Mag base sits flush with my P16-40 ( no mag funnel ) ... however the "beak" of the mag plastic base is more pronounced then the OEM P16-40 mag... I'd bet a little sanding will contour it to a better shape.

While I don't have a 9MM full size Para. to test feeding... a .40 HST would feed grudgingly into the 40 cal. barrel when fed from the 9MM mag.

I wouldn't recommend using the 9MM mag for your .40 pistol... but that did tell me the feed is most likely fine in a 9MM Para full size frame.

Anyway... $20 bucks a mag.... Off to find a 9MM conversion barrel for the P16-40

https://www.cdnnsports.com/remington-rp9-18rd-9mm-magazine.html?___SID=U