Liquid Volumetric Filling ⚫ Figure 20.8 shows three methods that are used to keep the product from leaking out around the piston as it moves back and forth: fine tolerance, rings placed in grooves around their circumference and cuffs applied to the ends of the pistons to create a seal.Liquid Volumetric Filling ⚫ Figure 20.8 shows three methods that are used to keep the product from leaking out around the piston as it moves back and forth: fine tolerance, rings placed in grooves around their circumference and cuffs applied to the ends of the pistons to create a seal