2.1" using the gg&g rail and low rings with a 32 mm objective scope. This is within .1" of my .308 bolt action using a 40mm objective scope. As you remember, I like a high HAB. Fit to you is key with all this stuff. For what I do with them, a 2" HAB works fine on Centerfire rifles, but it isn't how my .22 bolt action is setup (for contrast information.)