Range: 0 to 0.25 milligrams/liter20 foil sealed Copper test packetsInstant Ocean aquarium test kits make saltwater testing easier than ever before for the beginning hobbyist as well as the experienced aquarist. The one piece color chip comparator is easy to use. The durable wide-mouth holder has more room for adding the test chemicals and is stabilized to prevent spilling. Foil packets protect the granular test chemicals from light and moisture and keep them fresh indefinitely.