If you don't plan on running the NV rail, the 1.18" or whatever the lowest is will work and clear the barrel plenty due to the height of the factory rail. If you want to use the NV rail you'll need the same height as what you would use on the AX with continuos rail or an AR. I'm going to run the same mount on my AT when it gets here as I use on my AX so that I can swap scopes if one were to go down without changing anything else, and I also plan on running the NV rail with a NVD eventually.