The CB Tech Electronic Water Filter Capacity Monitor measures the number of gallons of water that flow through the filter and is used with the Multipure or CB Tech Undersink Water Filter (CBVOCSB, CB-VOC). Increases filter capacity by about 50% and will pay for itself in a few filter changes and indicates when to safely change your filter. Increases safe filter life to 1250 gallons for CBVOCSB undersink units. Includes all necessary fittings and an electronic LED faucet ring indicator to take the guesswork out of filter cartridge replacement.