Meprolight M21 Picatinny Rail Adaptor Black 21PR. The M21 Picatinny Rail Adaptor Mount System includes a top rail with cross slot and a bottom rail with cross slot. The Meprolight Picatinny Rail Adaptor Mount allows shooters to attach weapon lights and laser aiming devices to their M-series handguards. Be sure to see the full line of Meprolight weapon lights and accessories along with weapon mounts weapon lights accessories laser sights and other weapon accessories on our Meprolight page. Specifications for Meprolight M21 Picatinny Rail Adaptors: Manufacturer: Meprolight Color: Black Fabric/Material: Aluminum Red Dot Sights-Footprint: Not Applicable Optic Cut: Not Applicable Length: 8.3 in Width: 4.3 in Height: 1.7 in Weight: 0.38 lb Mount Type: Picatinny Gun Rail: Picatinny Package Contents: Meprolight M21 Picatinny Rail Adaptors Meprolight 5626020100: M21 Picatinny Rail Adaptor Black 21PR