The spring along with the plastic piece comes off the bottom piece. It's a tight fit, so just work the spring off.

Congrats on the win!!!
I saw that deal, and could have waited 3 days (but didn't know), but I got my k100 last night from aquavapor when it was more. I like it, tested out and popped by aga-t coil, must redo. Waiting on 2 cent fuse (just in case) and I need something for my threads, a bit rough and squeaks, button is nice, not over clicky. Tested out with 18350 charged and rested battery and it won't fire...sometimes. Wasn't sure how far to screw this down and have a tank on there meantime. I really have to press button in to get it to fire.
edit: gave up on tank, too high ohms, wasn't doing it. Switched to igo-l vape could be better, have to really work that button.
I tighten mine down fairly tight. I don't force it, but tighten till it stops, and the throw is pretty short, and easy to fire.
I saw that deal, and could have waited 3 days (but didn't know), but I got my k100 last night from aquavapor when it was more...
I thought about it, I ordered morning the 15th, and saw in the evening it was deal of the day, 5.00 less. Now it's $10.00 less than I paid as of yesterday and sold out, noticed less points also. You gotta balance it out somewhere I guess.

