This NIST-certified edition of the REED R3510 pairs the same slim, long-stem pH pen design with a NIST-traceable calibration certificate for documented accuracy. It measures 0 to 14 pH with automatic multi-point calibration and buffer recognition, displayed on a clear LCD, and is built to reach into narrow vessels like test tubes. The added certification suits regulated or quality-controlled environments where instrument traceability must be demonstrated on record.