These pH pens are highly stable, easy to use, waterproof, have a fast response time and show accurate readings on a large LCD display screen. They are designed for simple one-hand operation and will float if accidentally dropped in a liquid. The pens automatically calibrate to pH buffers 4, 7 and 10, and can also be adjusted to recognize non-standard buffers. Features include a hold function, auto power-off and a low battery indicator. Comes with 4 button-cell batteries and a built-in electrode with protective cap. Dimensions: 16.5 x 3.5 x 3.2 cm. Warranty 1 year.