Transparent flat gauge glass, also called transparent sight glass, transparent level glass and transparent level gauge, is usually made of borosilicate glass and aluminosilicate glass. The glass is manufactured into the strip shape and used in boiler or some instruments for observing the liquid level.

Reflex Gauge Glass, designed with a prismatic surface facing the liquid in a tank or boiler, enhances visibility, ideal for low to medium pressure applications. In contrast, Transparent Level Glass, a fully transparent material, allows for direct observation of the liquid, useful for color-indicating substances or applications requiring inspection of liquid characteristics. Though suitable for high-pressure applications, it tends to be more expensive and may need more maintenance due to occasional mica shield replacements.