Trijicon ACOG Rifle Scope 4x32 Dual Illuminated Red Horseshoe/Dot Reticle w/Colt Knob Thumscrew Mount Black 100581

From OpticsPlanet

Trijicon ACOG Rifle Scope 4x32 Dual Illuminated Red Horseshoe/Dot Reticle w/Colt Knob Thumscrew Mount Black 100581. To achieve this it uses a combination of fiber optics and self-luminious tritium allowing the aiming point to always be visible without the use of batteries. This is because the tritium illuminates the aiming point in total darkness while the fiber optic self-adjusts the reticle brightness during dayling according to ambient lighting conditions. This means you can keep both eyes open while acquiring targets and aiming through the optic even when you are moving between varying brightness levels.