... 65% heat increases 12% Higher temperature, more hot water Three target vacuum tubesJust like an automobile engine, the computer CPU, vacuum ... highest of vacuum tube working temperature as high as 300°C, effectively preventing the coating from bursting, aging, discoloring, function ... glass with coefficient of linear expansion 3.3×10-6/°C, complies with international ISO1776 acid proof Grade 1, ISO695 ...