The Angle Cosine Indicator, is a solid precision instrument, made from aircraft grade aluminium, which is anodized  in black. Its action is completely silent, it is robust and is unaffected by weather.  Above all, it is easy to use.

It is attached to the scope at 90 degrees from the bore, by the scope ring supplied, either in front of or behind the parallax adjustment knobs, depending on your eyesight preference.  It can be used on your scope, spotting scope, bow or binoculars. The ACI works on any shoulder mounted weapon system and on almost all types of optic.  The cosine marks go up in increments of 5 degrees starting at “0” so you can also work out the angle of the shot if you wish (making it compatible with most etched reticule based sighting systems, and also the Mildot Master).                                                  

When the weapon is held at an angle, the ACI  indicates the cosine number of that angle by means of a highly visible index mark;  for mathematical  simplicity you should treat these marks as decimal or percentages, whichever you find easier, hence 87 would be .87 or 87%.  The "Established Range" (distance to target at the indicated angle) is then multiplied by the reading.

WHAT DOES THIS DO?  IT GIVES THE ADJUSTED FOR GRAVITY DISTANCE