I bought one after positive reviews online. It's a polymer quad stack mag. Claims to be a 60 rounder. I could only load 58. Started good. Fired 40 rounds or so then it became a jam o matic. Frequent feed issues including double feeds. Ran a 30 round lancer through the gun problem free than reloaded and retried the smeisser. Lots of problems still. Probably about 20 failures in 60 rounds. The weird little bho tab did lock the bolt back at end. Packed up the mag and finished the day with Lancers and magpuls. Wanted to like the mag but it simply doesnt work.