Fast, accurate dissolved oxygen determinations with no mixing of reagents, no titrations and no expensive, electronic meters. Simply snap the tip of the pre-scored, self-filling reagent ampule in the water sample and in less than two minutes the color change has fully developed and is compared to the color standards. Includes one set of nine color standards from 1 to 12 ppm, sample cup, 30 test ampules, and complete illustrated instructions. The color standards have a shelf life of two years or more if protected from excessive light exposure. A refill kit of 30 test ampules is available separately.