20 MOA. I talked to a Leupold tech and he enlightened me about something I never thought about. As you adjust the turrets for elevation, the crosshairs are move into ever decreasing space in the scope tube. With the MOA mount, you will stay further away from the decreasing available windage adjustment. I don't understand why it does it, but he explained that if you do a ladder test, it could cause a horizontal error. as you move the crosshairs into the ever decreasing part of the scope. Like I said, I don't fully understand why it induces a horizontal error, but he is the expert.