The SB Tactical FS1913A-01-SB Folding Brace for M1913 Picatinny is a low-profile, left-side-folding brace assembly for platforms with an M1913 (Picatinny) interface at the receiver rear. Its strut design provides solid lock-up when extended.This complete assembly features an advanced steel hinge and 6061 aluminum strut, with locking positions for both folded storage and extended use.Advanced steel hinge locks in folded and extended positions.6061 aluminum strut construction.Fits rear M1913 interfaces on SIG MPX, SIG MCX, SIG Rattler, and Rock River LAR-PDS.Select the FS1913 for a compact folding configuration with defined lock-up at both positions; verify your receiver's M1913 interface before purchase.