The concept is simple; a durable scope with a reticle that illuminates in low light situations. And the best part is that it doesn't require batteries. Over 25 years later, the original ACOG stands the test of time and remains one of the most popular items. ACOG 4x32 Scope with Full Line Red Illumination features black crosshairs during daytime and tritium illuminates reticle at night. The reticle ranges out to 800 meters for 5.56 (.223 cal).