All my scopes have a flag bottom. Then this new scope I order came in and it have this thing on the bottom of the scope at an angle. Not sure what it is but I used a pliers and turn it counter clockwise and it came loose. I kept turning it and there is a spring inside that pushed the whole thing out. I was like wtf lol. I tried to screw it back but the spring was so hard. You have to really push it down and twist it back. Took me awhile but I was able to screw it back. So what the hell is this thing for? Why most scope don't have it and then there is this scope that have it.