I didn't know these existed. Would be cool to get one for my 40 but $140 is a little tough to swallow.The HK ones work fine in both 9mm and in the 40 although they only hold 27 in the .40. I have used them in my 9SD and my .40 Tac without issue. Aftermarket ProMags are not really good for anything other than practicing your clearing drills. They seem to work fine at first then the lips spread and the springs weaken then they are pretty much toast.
If you can find HK 31 round mags for $100 jump on them. I bought mine years ago at dealer discount pricing and paid $115 to $125. Now they are much more than that. Honestly though, pretty useless other than a range toy IMO.
Here ya go.Since I'm not gonna buy - Stokes classic arms on gun broker has one for $99. Have no idea how to do a link, so this is the best I can do lol