Waterproof pH Pens. Easy to use, rugged and economical pH pens. Features: Waterproof housing (meets IP67) protects meter from damage operating in a wet environment. Easy to calibrator single CAL key with automatic pH buffer recognition (4,7, and 10pH). Choice of 3 point calibration for better accuracy. Convenient pen size fits into your pocket. Data hold freezes reading on display. Low battery indicator. Auto power off saves battery life with disable function option. Complete with built in electrode, sensor cap, inner pH electrode protection cap, and 4 LR44 button batteries. pH range: 0 to 14pH. Temperature range: 32 to 122 deg F (0 to 50 deg C). Automatic Temperature Compensation. Dual LCD displays both pH and Temperature readings.