Magazines for 9mm roller locks are few and far between. Most suck it up and get German-made H&K mags but at $70 per magazine it adds up quick. There have been some attempts at polymer magazines for the venerable MP5 but they are hit or miss. Also finding a magazine with a capacity of over 30 rounds that isn’t a drum, is very hard. For over a year HK Parts had a windowed polymer magazine on their website but it was “coming soon”. Well, they are finally available. Let’s take a look at the AC-Unity MP5 magazines.