Im not to sure ian, but i would say about 3". There isnt much detail in the acompanying booklets. After mounting the scope, it did feel a little far away to me. So i added one of those eye exstention things, not the pigs ear one the tube type. This helped solve it. I have just removed this and replaced it with a butler creek, and it seems ok. I had no problems hitting a squirrel befor with it