The Magpul GEN. 3 Magazine coupler is made specifically for Magpul PMAG 30 round AR-15/M4 magazines. Attach two of the GEN. M3 4 rib magazines together for more efficient speed reloads, and to keep an additional 30 rounds of ammunition accessible on the weapon at all times. The Magpul coupler features a two-piece bolt on, durable, lightweight, polymer design. Bolt and nut are both included. Please see picture to reassure that this product will fit your magazines. WILL NOT FIT GEN MAGPUL GEN. 2 or GEN. 1 MAGAZINES.