Hach 173006 Colorwheel Glass Viewing Tubes are glass viewing tubes with a 5 mL mark. Typically two of these tubes are filled to the 5 ml mark with the water to be sampled. One of the tubes has a reagent added, causing the sample water to change color.
The tint of the sampled water is then compared to the tube that has had no reagent added through the colorwheel disc.
Hach 173006 Colorwheel Glass Viewing Tubes are sold per Pack of 6.