A reference solution used for adjusting nutrient Instruments. This is a Nutradip TDS Calibration Solution of 1000. When used with the 3 in 1 Tri-Meter™, this solution at 20 Celsius will read "100" on the model 102/202 and "200" on the 103/203 model Tri-Meter™. You can use this calibration solution for all TDS meters , just read the manufacturers calibration procedures. Please Read the calibration instructions for your instrument before calibrating. Comes in a 500 ml Bottle.