Is this more of a personal preference? What also confuses me is that the levels on the rail mounted versions are on the left side of the rifle and the scope mounted ones are on the right? I would think as a right hand shooter that the level being on the left side would be easier since having your left eye open you can look at the level whereas if the level was on the right side of the scope you would have to adjust your face slightly to look at the level on the right? All inputs appreciated.