I am looking to find a lens cover for my NF that flips all the way back like the Leupold Alumina caps do. Also I prefer them to thread into the scope. I have used the Butler Creek slip on covers which are ok but I have broken an objective cover off because it was sticking up open. I know it may have been a freak accident but I just wanted to see if they made someting simmilar to the aluminas or if the 50mm Alumina would fit the NF. The slip on will not fit nor will the bikini because my scope sits too close to my barrel on one rifle.