The m16 clone has a semi adjustable center pin.. meaning it doesnt screw in and out but it will push in and out.. If you have the cash i would recommend a nemesis, should be a new batch here soon.. They are kinda hard to get, but well worth it. Very well performing, and until you own one, you wont fully understand. Everything is flush due to the center pin screwing up and down. And no battery rattle because of a telescopic switch. It's the best investment i made in a while..
Edit: I keep forgetting to say this, but if you need anything, feel free to pm me.. if i don't know then we will learn together