The Angle Cosine Indicator (ACI) is an indispensable sniper tool for long distance precision shots when aiming up or downhill. The ACI helps you to easily calculate and correct the gravity's effect on your bullet's trajectory. The bubble level enables the shooter to understand if the gun is completely level. Our ERATAC mount with ACI and bubble level can be easily attached to our Universal interface. it is not necessary to alter the position of the scope. The position of the ACI is such that the red needle is visible even when using a scope with the illumination control on the left side and while already aiming. The position of the elevation turret remains always visible because of the lateral bubble level. This mount does not include the ACI. Click Here, to view our selection of ACI's from Sniper Tools Design Company. ERA-TAC ERATAC Adapter w/Bubble Level T0940-0000