Reflex level gauge glass and transparent level gauge glasses standard in tempered borosilicate glass according to DIN7081 standard,This toughened safety glass is resistant to alkaline and acid medium and brine and high temperatures (max. 350° C, depending on the medium and any mica protection of the glass).If you want more resistant to pressure glass,we will use aluminosilicate glass for you,we also make the quartz glass for you resist to high temperature to max. 1100° C.