Ultimate Arms Gear Aluminum Weaver Picatinny Rail Light Laser Barrel Mount For Mossberg 500 590 835 Maverick 12 & 20 Gauge Shotgun Connects directly to your shotgun barrel or shotshell tubes from .75" - 1.1" diameter No Hassle Quick Installation - Easiest Way To Add a Tactical Accessory To A Shotgun Provides A 3 Slot Weaver-Picatinny Rail (Standard 7/8" wide) ; Length- 1.6" Precision Machined Aircraft Grade Aluminum Construction