Redline gauge glass tube is a typical kind of glass tube for glass tube gauges.

Redline glass tube has a red stripe in between two white stripes which makes a colorless liquid visible. It is widely used in liquid level gauge applications such as steam boilers and liquid tanks. Redline gauge glass tube is made of borosilicate glass which is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glass tubes are known for having very low coefficients of thermal expansion (3.3 × 10−6 K−1 at 20 °C), making them more resistant to thermal shock than any other common glass. Borosilicate glass tube is usually used in tubular level gauge for high temperature and pressure resistance, which is also known as tubular gauge glass, pyrex glass tube.