A validation for the performance of liquid particle counters with Thermo Scientific™ Validex™ Count Precision Size Standards. Excellent for instrument calibration and verification in the drinking water industry and for low level liquid particle counting and calibration. This product contains NIST™-traceable polymer particles packaged in ultrapure water at concentrations ideal for use in validating the performance of liquid particle counters. Particle counting in the drinking water industry has rapidly become an indispensable technology for optimizing water quality. The majority of particle counters used in the drinking water industry operate on the principle of single particle light obscuration.