1235-12-D is a series 1235 Flex-Tube® well type manometer. It is designed to meet the need for a direct reading single column instrument providing highly accurate pressure readings, positive, negative or differential. Unlike other makes, Dwyer manometer has no hidden wells or packing glands. This instrument is constructed of shatter-proof clear plastic tubing permanently bonded to well assemblies with leak-proof glued joints. Well assembly is precisely machined from solid acrylic plastic. Over-pressure safety trap assures protection against loss of fluid. Scale is adjusted with quick-acting positive mechanism.