tempered borosilicate sight glass -use for fireplace,light,or sightlevelglass -many size available -withstand 600 C tempered borosilicate sight glass-can be as sight gauge glass, oil sight glass,tank sight glass, flange sight glass,boiler sight glass,-for light,machine etc-flat,clear,smooth,high quality-withstand 600 centigrade degree.safe and durable-tempered,solid-many size and shape are ...