It works a little easier if you put the top half on the scope then slide them into place after you set the scope in the bottom part. As opposed to trying to hook the ring and get it over the tube at the same time. They are very strong rings, but today there are too many other cheap options that work better and pose less of a threat to scratch the tube during assembly. Sgtt's suggestion to spread the top is a good idea, but just go only as far as needed no farther