Mine was actually a brass button with threads. It has a brass nut on top (to make contact with the battery) that allows for adjustment. It is a poor design. I had to use a file and small brass washers to make it work. I spent hours getting it all to fit correctly.
I then purchased the 4nine clone (with a magnetic button), and it worked right out of the box. So I put the GP Paps (cheap clone) to the side.
Now all I have to adjust is the bottom pin of my 454 Big Block clone to shorten the throw, and it makes good contact. If i get any heat, it is from chain vaping, when this occurs, my head is spinning and I have to put it down.