HI. I'm new here....figured I'd make my first post.
yes, as pictured, the difference in the 10 vs 15 rnd 9mm mags is the groove making it a single stack mag.
now, on the .40 cal mags from the 96 model guns, the difference in the 10 rnd vs 11 rd mags, is that the 10 round mags have a longer bottom on the follower, so that it bottoms out against the bottom of the magazine preventing you from getting 10 rounds into it.
swap this out from a 11 rnd magazine, or cut the bottom of the follower off (most of them are just composite plastic) you can make the 10 round magazine an 11 round magazine....however...this may be a violation of laws...not sure now that the 1994 crime bill is expired.