Ppm

YD 1L Digital Salinity PPM Meter for Salt Water Pool
US $115.20
Waterproof 4 in1 Hydroponics Nutrient EC ppm CF Meter Soil Conductivity Tester
US $23.48
Waterproof 4 in1 Hydroponics Nutrient EC ppm CF Meter Soil Conductivity Tester
US $20.23