Matched sets of Nessler Comparison Tubes with Stoppers Caps - The graduation lines of all the nessler color comparison tubes in a matched set will not vary by more than 1.5 mm for the 50 mL and 2.0 mm for the 100 ml sizes, from that of any other tube in the set. The distance of these lines from the bottom of the tube may be anywhere within the scale lengths shown in the table below. 50 mL is available as a Cases of 6 and the 50/100 mL is available as a Cases of 12.Narrower and taller with a much longer scale length than the Low Form Nessler Tubes, these matched set Nessler Tubes come with cap style stoppers that need not be removed when making readings. The word "Shadowless" is printed on the side of the stopper to distinguish between regular weighing bottle stoppers of the same size. Tubes feature a "Shadowless Bottom" and durable white ceramic enamel rings and legend. Caps Included.