Simple-to-use test tube pH pen is designed for one-handed operation. Highly stable and accurate readings with a large LCD display, it automatically calibrates to pH 4, 7 and 10 buffers and can be adjusted to recognize non-standard buffers as well. Features hold function and auto power-off with low battery indicator. The case is IP65 waterproof and will float if accidentally dropped into the water. Comes with 2 button-cell batteries and a built-in electrode that is kept moist with a protective cap.