Humidity Calibration Kit for your Extech Digital Hygro-Thermometer.

Two bottles are included, one for the 75% relative humidity reference and one for the 33% relative humidity reference. The 75% relative humidity reference uses Sodium Chloride (NaCl) to produce the standard. The 33% Relative Humidity reference uses Magnesium Chloride (MgCl). Instructions for calibrating Extech instruments humidity meters are supplied with the humidity meter. Bottles designed with small opening for snugged fit of the sensor.