The Bindon Aiming Concept (BAC) is a both-eyes-open aiming method which allows shooters to acquire, track and hit targets more accurately than with one-eye-closed riflescopes.

ACOG TA31F 4x32 Scope with Red Chevron BAC Flattop Reticle- includes Flat Top Adapter. The chevron reticle is designed to be zeroed using the tip at 100 meters. The width of the chevron at the base is 5.53 MOA which is 19 in. at 300 meters. This allows range estimation for silhouette targets. Features dual illumination (Fiber optics provides  daylight illumination and tritium illuminates reticle at night). The ranging reticle is calibrated for 5.56(.223 cal) flattop
rifles out to 800 meters.

With its dual-illuminated reticle, the Trijicon ACOG TA31F provides shooters with a distinct aiming point in all light  conditions – without batteries.  Powered by a tritium-phosphor lamp, the scope’s reticle glows in low-light  conditions, while advanced fiber optics automatically adjust the brightness level and contrast of the reticle in brighter light conditions.  Many models – including the 4x32 ACOG TA31F that’s now available to hunters and target shooters – incorporate the innovative Bindon Aiming Concept™ (BAC). This revolutionary, both-eyes-open aiming method provides you with “instinctive” target acquisition and increased hit potential. And, the scope’s ranging is built into many of its reticles, allowing you to set zero and never worry about it again.  Broad-band, anti-reflective coated lenses provide superior clarity and light gathering capabilities with zero distortion. The ACOG TA31F also offers large eye volume, giving you greater leeway – fore and aft, and from side to side – with which to see through the lens. Of course, once the target is acquired, the ACOG TA31F is a trusted ally to help you zero in on a perfect shot. 

The ACOG TA31F is crafted with a tough, military-grade aluminum-alloy housing and is waterproof to depths of 328 feet – making it nearly indestructible. Only the prism housing moves, so it’s much more rugged than conventional designs. And the ACOG TA31F does not require failure-prone batteries – so you can rely on it to perform in practically every situation.