Mesa Tactical Receiver Mount Picatinny Rail Length: 4.5" Mossberg rails attach directly to the receivers of late-model (1997 and later) Mossberg shotguns with pre-tapped holes. These rails can only be fitted to later-model Mossbergs featuring factory tapped holes in the receiver. Standard profile rails are for general purpose optics mounting applications. These rails adhere to the minimum height requirement of the MIL-STD-1913 specification, and should not be used for mounting optics with the High-tube telescoping stock adapters. Tall Profile rails are only for use with Mesa Tactical telescoping stock adapters. These rails allow easy access to the Mossberg safety switch. These rails can be installed on other shotguns by tapping the top of the shotgun receiver with #8-40 UNS threads. Consult a gunsmith.