The Mag coupler for PMAG 30 and 40 round AR/M4 magazines which allows the user to attach two magazines together for more efficient speed reloads and to keep additional ammunition accessible on the weapon at all times. It features a two-piece bolt on design and durable lightweight reinforced polymer construction. made in specialized factoriesFits 5.56x45 PMAG 30 and 40 round AR/M4 GEN M2 MOE and AR/M4 GEN M3 magazinesImpact resistant polymerWide-set two-piece bolt-on designIntegral grooves interface with PMAG ribbing. NOTE: This Mag Coupler is NOT compatible with first generation PMAGs (with Black follower circa 2007-2009) 10 or 20 round PMAGs custom branded PMAGs or any other non AR15/M4 specific Magpul magazine such as the EMAG PMAG 30G or PMAG 30 AUS. Will also not fit other larger caliber magazines such as 7.62x39 and 7.62x51 PMAGS or any metal magazine.