I came across these mag couplers when searching for a product to couple my state restricted 10 round magazines. I had tried Caldwell magazine couplers but they did not work with the Magpul magazines. The RJK couplers worked perfectly with my Magpul magazines. Easy to install and the install video on the website was a great help. Since the coupled magazines will be used in my DFNDR plate carrier, it is a good idea to get Magpul dust/impact covers to place over the end of exposed magazine to protect the cartridge in the magazine that will be sticking out of the top of the magazine pouch on the carrier.