4 Pack Vacuum Cleaner HEPA Filters for Cyclonic Series RO3753EA RO3731EA RO3786EA 100% new with high quality and good price.For checking TDS/salt (NaCl) levels freshwater aquariums, ponds and water purification systems.3-in-1 smart pen combines TDS, , and a temperature meter for improved accuracy.With an Automatic Temperature Compensation and the measuring range of 0-9999 ppm +/- 2%.4 Display modes: Press SHIFT button: TDS - ppm & Celsius, - s/cm & Celsius, TDS - ppm & Fahrenheit, - s/cm & Fahrenheit.Lock function, easy to read and record, press HOLD button then remove from test solution.The instrument will automatically shut down after 5 min of inactivity.Conductivity: 0 - 9999s/cmTDS: 0 - 9999ppmDegrees Celsius: 0.1 - 80.0 CelsiusFahrenheit: 32.0 - 176.0 FahrenheitResolution: TDS: 1ppm; : 1s/cmBattery: 1x3.0V (CR2032)Accuracy: 2%Colour:WhiteMaterial:plasticSize:152 x 30 x 14mmPackage Contents:1 x TDS & MeterOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.