Joe, don't go away mad. I mean Accucraft was so worried about this that they recalled all their K28 tanks and replace them because they didn't pass some extreme test. I know some have documented rupturing their K27 tanks by putting water that was too hot in the tender around the fuel tank. Some countries, I believe, require these tanks to pass what I would call extreme tests. The problem is in the real world, even though the instructions say use butane only, people will put all kinds of fuel mixes in these tanks and subject them to pressures they are not designed for. You may not of course. But, if you have this tank in the tender and put warm or hot water around it on a cold day, the fuel pressure goes up very quickly. If there is a weak point it will definitely rupture.