Features Measures all types of copper to less than 0.01 mg/L Multi-cavity plate for simultaneous testing of up to 6 tests at the same time Includes reference for test validation Marine or Freshwater Copper kits are usually of two types: compleximetric or titration based. Some kits measure only ionic copper and others measure both ionic and chelated copper. This kit uses a highly sensitive catalytic compleximetric based procedure to measure all types of copper to less than 0.01 mg/L in marine or freshwater. MultiTest™ Copper performs over 75 tests and contains a reference sample for validation. Features 75 Tests MultiTest™: Copper performs over 75 tests And with the multi-cavity test plate, multiple tests can be run at the same time. Accuracy Range - Measures between 0–0.80 mg/L copper Precision - Detectable changes on the color chart in 0.025mg/L & 0.0025 mg/L increments. Reference Sample - It isn't necessary to run a reference test to use this kit; however, its proper performance can be validated by running a test in the normal manner except that the reference sample is used in place of aquarium sample. You might choose to run a reference test if you have cause to believe the test is giving incorrect results. Color Chart All MultiTest™ test kits come with an easy-to-read color chart. It features a 5 cm viewing window to help isolate color and match as closely as possible to the test sample Opaque Multi-Cavity Test Plate All MultiTest™ test kits are read from an opaque white test plate. The sliding color chart along with the six-cavity test plate allows for easy reading and comparisons of several samples at the same time.