This has a floating 510 pin, you have to screw your squonking atty on first then screw this to your mod.
I put it on a mod first and sat it on my desk whilst I was looking for an rda to put on it, I returned about 45 seconds later with an rda I picked up the tube mod and it was really hot, I quickly unscrewed the switch cap to remove the battery when I unscrewed this contraption from my mech tube I found the positive pin was level with the negative thread of the 510 which was causing a short with the 510 of the mech mod.
Lucky the battery did not vent however it was freshly charged and after it cooled down I checked the voltage and it was at 3.9V.
If you screw your rda on first the floating 510 positive pin is lowered enough to make contact safely with the 510 of the mech mod.