Have not counted them...yet...but first I need to correct an error I made in reviewing the Defender II 50 w.
Both you and I reported that the GS Air, or the M, or both didn't sit flush on top of the Defender. We may have assumed ---at least I did--- that this was a design issue with the mod.
I was wrong...it's a function of the length of the threaded base of the GS Air and /or M.
I have a GS-tank sitting on the Defender now, absolutely flush with the top of the mod.
Sorry for the previous misinformation.
Back to your question, Linda..There are four threads.
Another review amendment- three times today it has switched from watts to volts. I'm not sure why. I didn't have it locked. My bad. I did have it in my jeans pocket. My dumb.
I'll lock it tomorrow and see if it is the culprit, or if I am.
Thanks, Gran! Looks like the number of threads is about the same (minimal, basically). I guess that's one of the reasons these tanks are so cheap.
Regarding the Defender, mine still changes from watts to volts occasionally, but I'm really not sure if it's user error or a glitch with the mod. It always does it when I'm concentrating on something else. But if it's happening to you, too, that gives me pause. That's interesting that the base connection is shorter on the GS Tank. I wonder if that would cause a connection issue on mods that don't have a spring-loaded 510.