The sunken Colorado pan is square, 0.92 m (3 ft) on a side and 0.46 m (18 in.) deep and made of unpainted galvanized iron.  As the name suggests, it is buried in the ground to within about 5 cm (2 in.) of its rim. Evaporation from a Sunken Colorado Pan can be compared with a Class A pan using conversion constants. The pan coefficient, on an annual basis, is about 0.8.