Precise electronic two channel vacuum meter Designed specifically for the intake synchronization of carbureted or fuel injected multi-cylinder engines Reads actual vacuum value as well as comparative vacuum values Mercury-free design allows operation in any position Electronic damping averages vacuum readings and displays on bright LED Accurate to within 0.2 cm/Hg (centimeters of mercury vacuum) True resolution with no friction or inertia that is commonly associated with mechanical synchronization devices Unaffected by barometric pressure changes Built-in tachometer for setting and monitoring engine RPM Dual channel design can synchronize 3 and 4 cylinder engines with optional 4-channel adapter ZZ92037 Powered by an external 12-volt source such as a bench battery or vehicle battery Includes 5mm and 6mm sets of rigid threaded carburetor adapters Soft carry/storage case ZZ91212 sold separately