The Advanced Fiber Optic Sight System is completely battery free, exhibiting the newest technology in tactical sight options. This is a 4X Magnified, aircraft grade annodized aluminum constructed sight for toughness and durability. The fiber optic cable, exposed at the sights top, collects and transfers light into a simple paralax free mil spec crosshairs reticle. Your choice of a green or red dot so please specify when ordering. Attaches easily and quickly with the two thumb screws and will mount to all standard picatinny or weaver rails.