Magpul Industries Universal Carbine Stock, Fits 1913 Picatinny Rail, Side Folding, Adjustable Length of Pull, Matte Finish, Flat Dark Earth MAG1441-FDE The Magpul UCS (Universal Carbine Stock) is designed to be the ideal supplement to the vast array of firearms utilizing a vertical M1913 Picatinny rail on the rear of the receiver for stock fitment. To accommodate the wide variety of charging handles styles, ejection port locations, and control locations, the UCS features a reversible hinge for left and right folding configurations, and five degrees of drop for clearance.