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 reticle designed for the Los Angeles Police Department. The scope features crosshairs during daytime and tritium illuminates reticle at night.