The PRFCS Polymer Picatinny Rail for Collapsible Stock allows the ability of mounting an Adjustable Checkpiece (ACP) or the 12 Gauge Shotgun Shell Holder SSM or a variety of other rail mounted accessories. It�s solidly constructed of rugged fiberglass reinforced high-density polymer to provide a lifetime of heavy use. It mounts thru the sling opening adding the versatility of a Picatinny rail to your existing stock. - Installs instantly on most collapsible stocks - 3'' Solid side Picatinny rail allows an additional Adjustable Checkpiece (ACP) or a 12 Gauge Shotgun Shell Holder (SSM) - Made with Polymer - Adjustment lever with easy installation