Cannon 9721-E71 Model CFOU-350 Size 350 Cannon-Fenske Opaque Viscometer Tube, Uncalibrated. This Cannon-Fenske Opaque Viscometer measures kinematic viscosity of transparent and opaque Newtonian liquids according to ASTM D445, ISO 3104 and ASTM D2170. Minimum sample volume is 12 mL. Minimum bath depth is 230 mm (9 in). These viscometers are uncalibrated. Holders are sold separately.