3.3 borosilicate sight glass -for light,machine etc -flat,clear,smooth -withstand 600 centigrade degree -tempered,solid 3.3 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 ...