Reflex liquid level gauge has a sturdily constructed body, with the glass and cover securely held by U-bolts to maintain a hermetic seal (see figure below). This type of level gauge features several parallel grooves cut into the glass surface that is in contact with the liquid. The resulting prismatic diffraction gases to appear white by reflection : liquids black by absorption thus the level of even transparent liquids can be clearly observed. Low-medium and high-pressure type may be used according to application conditions and units may be manufactured using carbon steel, stainless steel or a wide variety of other materials for parts in contact with the liquid. Type L100 reflex gauges have a number of further advantages including light weight, availability of long visible lengths and low price.