Use the Weaver Optics Thumb Nut Flattop Riser Rail for AR-15/M16 to achieve optimal eye relief and height. This multi-slot flat top riser is designed for AR-15 and M16 platforms, and features a lightweight and durable 6061-T6 aluminum construction. To help you mount it without any tools, the riser has two finger-operated thumbscrews. Product Features For Flattop AR-15/M16 Platforms Multi-Slot Design Finger-Operated Thumbscrews 6061-T6 Aluminum Construction