The HI98103 Checker pH tester has been designed with many advanced features while maintaining the look and feel of the original Checker. The redesigned Checker now offers automatic calibration to one or two points, automatic buffer recognition, calibrated buffer tags, stability indicator, low battery indicator, and selectable automatic shut off. The Checker plus still maintains the iconic pentagon design with a probe that measures 103 mm in length and tapered to a 8 mm diameter making it ideal for test tubes and vials.