Ultimate Arms Gear Pistol Handgun Scope Mount for Sights, Lasers, Lights & Accessories Fits Smith and Wesson S & W 1911 M&P SD9 SD40 Pistols Constructed from Precision Machined Aircraft Grade Aluminum Alloy. Fits on Most Pistol Accessory to Provide a Solid Style Platform for Most Optics. Provides A Standard 7/8" 12 Slot Top See-Thru Designed & 3 Slot Bottom - For Attaching Scopes, Sights, light, lasers etc. Specifications: Length 5" inches. Weight 3 oz. Easy to Install. 2 Set Screws Lock Tight to Existing Rail.