In this article we tell you what Minute of Angle (MOA) is and how to calculate it. Moreover, how to maintain zero with your rifle if the magnification of the sight changes.
Vector Optics Sentinel 6-24x50mm, 1/8 MOA, 30 mm Tube, Red & Green Illuminated Second Focal Plane (SFP) Riflescope : Amazon.ca: Electronics
Hawke Interchangeable Turrets 1/8 MOA - Camera Land NY