Trust us, not all PH pens are born equal. We have been through our fair share of Ebay cheapies! This PH meter is the ultimate brewing tool designed by the American company Extech; completely waterproof, measuring PH from 0.0 to 14.0pH and temperature from 0 degrees Celsius to 50 degrees Celsius, adjusting the PH reading automatically according to Temperature. Automatic pH buffer recognition (4.7, and 10PH).