The Bluelab pH Pen is the latest innovation for hand-held meters. It provides a compact, quick and handy way to manage the success of crops, to ensure maximum uptake of nutrients. Teamed with the Bluelab EC Pen or Bluelab ppm Pen, it is a handy, convenient and accurate system for ensuring optimum plant growth and health. Features Measures pH and temperature. Selectable units for °C & °F. Backlit LCD display. Double junction probe (not replaceable). Successful pH calibration indicator. Hold function. Low battery warning. Fully waterproof. Auto off function. Automatic temperature compensation.