The Sure Test? Base Plus pH Pen combines performance with affordability. Reads both pH and temperature (?F or ?C) with automatic temperature compensation (ATC) for more reliable pH measurements. Features a pH resolution of 0.01 and an impressive pH accuracy of +/- 0.05. Single touch auto buffer recognition for easy, error-free calibration. Waterproof housing (IP65 rated). Comes with 4x LR44 batteries.