I often wonder where my brain goes when a vaping problem crops up ... this might help others who share my brain challanged senior moments ... Certain clearos like the Freemax Starre fill by both the glass and its stainless coller unscrewing as one piece instead of just by threads as many plastic tanks use . No matter how carefully I was lightly tightening the glass tank and coller, I couldn't remove it for the next fill up. Shamed to admit it never occurred to me the hot pyrex and stainless coller were simply too hot ... cool by blowing , by water, by waiting, or even 4 minutes in the freezer and it easily unscrews. This I imagine is more an occurrence for those who sub vape and use 50 to 220 watt boxes.