The Flatline Ops Military Spec Angle Cosine Indicator® (ACI®) takes the guesswork out of uphill and downhill precision shooting. An angle cosine indicator is a simple tool for hunters to use in mountainous terrain to obtain their corrected for gravity distance to target. The “Mil Spec” ACI is a vault solid, waterproof, precision instrument; silent (per Military Specs), and made from aircraft grade aluminum, which is anodized in a flat black color.

The cosine numbers are laser engraved onto the body in five degree increments. The lens is shatterproof, shockproof, and resistant to chemicals such as acetone and cleaning solvents. Completely mechanical, there are no batteries or electronics to fail. This version of the ACI is guaranteed watertight and is manufactured per US Military Directives.