It does seem to look a bit different than your standard P226/Beretta92 mag design - those seem to slim down right before the top round of the mag, while the 365/Hellcat look to slim down 2-3 rds earlier. I could see how that is the innovation that allows them to be as skinny as a single-stack yet hold quite a bit more ammo - you basically are a single stack for the top few inches of the mag, so more room to stuff the action in there, while the empty grip below can hold doublestacked cartridges for a few inches, going from 6-7rds in a single stack gun to 10-12 in this one, without adding much if any bulk. Very neat idea. The fact that even the Hellcat has successfully undergone 10k+rd torture tests and survived (with just regular recoil spring changes IIRC) is pretty remarkable. For ages, if you wanted a reliable pocket gun it's the j-frame or nothing, now you have options that are more rugged than many of the early fullsize 9mms and not much heavier than a j-frame, with double the capacity or more. Plus, many will even mount a red dot, so you have something capable of much easier longer distance reach as well - 10yds and over, red dots on pistols start to be pretty awesome. While I'm extremely biased against striker fired anything due to safety/NPE concerns, it's quite an accomplishment to have something that light, that small, that cheap, that reliable.
The hotness when I started on gun forums for itty bitty 9mm pistols was the Kahr series, and they weren't terribly reliable, and I remember all the threads about how you had to break the things in.
