The Leupold Zero Point Boresighter has a unique lens aperture system that eliminates point of aim errors from parallax due to extreme misalignment and allows you to get your riflescope on target fast. Precise collimation of the prismatic optical system provides accurate measurement of where your riflescope is aimed, regardless of where the boresighter is placed on the muzzle. The powerful neodymium magnetic attachment works for nearly all firearms and all calibers without the need for separate arbors. The Leupold boresighter also includes natural backlighting of the target, LED illumination for use in low light settings and an inch scale for measuring approximate riflescope height and target group sizes. The Leupold Zero Point Boresighter is powered by a single battery (included) which yields approximately 25 hours of battery life and includes range cards for recording sight-in information.