Orifice-meter and Mouthpiece allows hydrologists and engineers a simple method of measuring the Coefficient of Discharge, Coefficient of Contraction and Coefficient of Velocity in variable heads. The apparatus is used to calibrate the following types of Orifice-meters and Mouthpieces:- • Orifice-meter - 16 & 12 mm • Mouthpieces - 18 & 14 mm