Extreme Accuracy. Easy to Test in 4 Steps - Zero the Checker, Add a regent to your water sample, Insert the Vile in the Checker, Read the Numbered Results. BOOM EASY. ZAIR. Zero, Add, Insert, Read. INCLUDES REAGENTS FOR 6X TESTS. The Hanna Phosphate Low Range Checker ®  bridges the gap between simple chemical test kits and professional instrumentation. Chemical test kits have limited accuracy and resolution since they rely upon the human eye to discern differences in color. Professional instrumentation incorporates a light source such as an LED or tungsten lamp with a filter and a light sensing detector to precisely determine ion concentration. Professional instrumentation offers greater resolution and accuracy but can cost hundreds of dollars. The Hanna Phosphate Low Range Checker ®  uses a fixed wavelength LED and silicon photo detector to provide the accuracy of professional instrumentation at the affordable price of a chemical test kit. *To zero 1 ml of reagent A is added to deionized/distilled water as a blank. Features at-a-glance: Easier to use and more accurate than chemical test kits Dedicated to a single parameter Small size, big convenience Ideal for: Aquaculture, Water Quality, Environmental, Education  HI713 Checker® is supplied with (2) sample cuvettes with caps, phosphate LR reagent starter kit for 6 tests (6 powder reagent packets), battery, instructions and quick start guide.   Range: 0.00 to 2.50 ppm (mg/L) Resolution: 0.01 ppm (mg/L) Precision: ±0.04 ppm (mg/L) ±4% of reading @ 25°C Light Source: LED @ 525 nm Light Detector: Silicon photocell Environment: 0 to 50°C (32 to 122°F); RH max 95% non-condensing Battery Type: (1) 1.5V AAA Auto-off: After 2 minutes of non-use and after read Dimensions: 81.5 x 61 x 37.5 mm (3.2 x 2.4 x 1.5") Weight: 64 g (2.25 oz.) Method: Adaptation of Standard Method 4500-P E.