First: You should post this in the Armory section of ARFCOM
Second: When you get your answer, post in the Want to Buy section of the Equipment Exchange
Third: before you go to either of the above, you need to determine the size of the main tube of the scope to match it to a set of rings. 40mm is your Obj. size, not your tube size. It is more htan likely a 1" or 30 mm tube. If you do not know, post in the optics section with the type of scope you have, maker, model number, power settings, obj. size and someone will let you know the tube size.