The Baum Pocket Aneroid is a 300 mmHg portable instrument. It's built to agree with our master instruments, which are traceable to the United States National Institute of Standards and Technology. It complies with ANSI/AAMI SP-9 for accuracy and performance (1% full scale +/- 3 mmHg). The unique, high contrast scale and red pointer increase visibility and reduce parallax error. They are manufactured with a precision low friction movement and twin pre-seasoned phosphor-bronze diaphragm capsules.