Diamondhead USA Polymer Front and Rear Flip Up Sights with NiteBrite and Diamond Integrated Sighting System Advanced polymer composite material for strength, light weight & exceptional durability; LIFETIME WARRANTY NiteBrite photoluminescent inserts (the low-cost alternative to Tritium) can be charged by natural light or with a flashlight Spring-loaded sights flip up quickly with the push of a button, stay up securely and fold down flat as back up sights Patented diamond-shaped apertures and upper housings for fast alignment Secure attachment to all Mil. Std. 1913 Picatinny Rails.