Also known as Zahn cups, these testers let you calculate viscosity based on the speed at which a liquid drains through a cup with a hole at the bottom. To determine viscosity, dip the cup in a liquid until it is completely filled, lift the cup out of the liquid, and time how many seconds it takes for the liquid to drain out of the hole in the bottom. Use the included formula to convert seconds to centipoise. Testers cannot be sold to Canada due to import regulations.