Like the Lage MAX-11 uppers, it also slows down the rate of fire to around 650 RPM (a faster 900 RPM bolt is also available), and in combination with the longer bolt travel, the gun is much more manageable and accurate for short bursts and follow up shots. They provide a carbine length upper that allows the shooter to use inexpensive high-capacity 72-round Suomi M31 drum magazines, or Suomi 50-round "coffin" mags. Other than having an approximately 2" length difference suited to the two different lower receivers, they are otherwise identical. The MAX-31 and -31A are 9mm accessory uppers from Lage Manufacturing for the M11/NINE and M11A1. It was such a fun upper to shoot and such high quality, that I got on the list for their MAX-31A upper, which similarly became available a few months later and arrived at my door within days of my payment. But I still wanted it, ponied up the money, and a few days later it arrived. One of the nice things about the waiting lists at Lage Manufacturing is that you don't have to pre-pay and you're under no obligation. A few months later, I was told that mine was ready to ship if I still wanted it. 380 gun (this was before I later bought an M11/NINE). Shortly after getting my SWD M11A1, I got on the list for a MAX-11A/9mm upper for it so that I could add 9mm capability to the. LAGE MAX-31 DRUM FEED UPPER FOR THE M-11 review by Concorde Practical Solutions Folding UZI stock for the M-11