My only complaint about my protank2 is that the o ring goes bad before the atomizer. The kit that I bought came with 2 extras but I need more. From what I can see there are 4 o rings: 2 large ones that seal the glass tank, a tiny white rubber one on the bottom of the atomizer and a slightly larger one above that. That's the one that I need. I've searched but all I can find are the large ones. Obviously they go bad quickly if the company put 2 extras in the kit. (the kit came with 2 atomizers and 2 o rings)