Allow the attachment of all standard 21mm picatinny specrail-mounted accessories.Can position just enough rail area exactly where you need it for each accessory, available in six lengthsInstall These Screws by Allen Wrench Tool, Simple To Install or Remove. Pack Of 7-Slot,7-Slot,5-Slot,5-Slot,3-Slot,3-Slot Solid Rails, 13 Sets Matched Screws, 13 Sets Locking T-Nuts and 2Allen Wrench .Ultralight rail with solid polymer construction and low profile design reduces bulk. 7-Slot 0.36Oz, 5-Slot 0.28Oz, 3-Slot 0.19Oz, much lighter than aluminum alloy, high strength and good safety, The material is installed on the metal surface without causing damage to the main structureInjection molded from a proprietary reinforced composite for enhanced strength and durability while remaining lightweight, Rail Sections also feature beveled ends to reduce snagging and eliminate sharp corners and edges.", Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.