I think was Brownells website had actual dimensions for various scope ring brands - I found that "Low", "Medium", "High", "Extra High" words vary a lot by one ring maker to another - since you have the scope, base and rifle in hand - should be able to mock up something to tell you the dimension that you need? I also noticed some makers give dimension from top of base to bottom of scope tube - others top of base to the middle of the scope ring - so want to pay attention to what you work with?