Five sizes of Asphalt Institute Viscometers are available to measure highly viscous materials such as bitumen. The elapsed time for a fixed volume of liquid to be drawn through capillary tube is multiplied by a constant to determine absolute viscosity. A minimum sample size of 3ml, and a bath depth of 7in (180mm) are required. A certificate of calibration is included. Neoprene rubber holders to fit a 2in (51mm) diameter hole are ordered separately as PTA-100.