When I first received it, it wouldn't hold zero. My rifle was averaging a 2.5" group @100 yards and changing POI between groups. After spending almost $300 on different types of ammo (stupidity on my part) I decided to send it back to Leupold. They said it had an internal lens that was loose, and the erector was not functioning properly. They fixed it and send it back to me within a week since it was NIB. Upon arriving back, the parallax knob was not functioning like before. It now stops about 1/2 of a turn beyond infinity and when setting for 100 yards, the reference on the knob reads over 300 yards. I mounted and shot it just to verify functionality of the erector system and it shot great for about a dozen rounds. I was getting 1/2 MOA groups without problem, until it lost zero again. I've been a long time user of Leupold, but do not plan on purchasing another one after this experience with them.