The REED R3510 is a compact pen-style pH meter with an extended slim probe, well suited to reaching into narrow test tubes, vials, and sample containers. It reads 0 to 14 pH with roughly +/-0.2 pH accuracy, supports automatic one-, two-, or three-point calibration with buffer recognition, and displays readings on a clear LCD. A protective storage cap keeps the electrode moist between uses, and it runs on a pair of coin-cell batteries with auto shut-off to save power.