This switch is approximately 4 inches in diameter and its NSN is 5930-00-831-7642. It can operate on a medium of air and is adjusted to 237 knots (2.776 in Hg gage) ± 5 knots (± .122 in Hg gage). Also, it is adjustable from 180 to 240 knots and is used primarily on the F-4 and other military aircraft.