Keeping your scope perfectly aligned is critical to long-range accuracy. Canting your scope, even just a couple of degrees, can cause error in point of impact. With modern "Drop-Compensating" scopes, an Anti-Cant Indicator is a necessity. The WheelerAA(R) Anti-Cant Indicator ensures that your rifle is always held near perfectly vertical, eliminating any chance for "Cant Error" to cause a miss.