You may want to consider a cantilever mount. This picture shows a conventional mount, which means because of the length of the scope the eyepiece is at least an 1 1/2 inches past the rear of the receiver. If you have a lot of time with ARs and this is your first scope you'll find yourself planting your eyeball into the rear of the scope until you get used to it. The cantilever mount prevents this. Also if you end up going to a larger caliber AR, say AR10, you'll definitely want cantilever mounts to prevent scope eye.