Watts Model 994HMB / 994BLT Portable Hydrant Meter Backflow Preventers prevent the reverse flow of polluted water from entering into the potable water supply where flow is in one direction and the possibility of cross-connections exists, such as at a fire hydrant or other non-permanent installation. It consists of a stainless steel body construction with stainless steel internal parts, meter housing, measuring element, and permanently sealed register to measure flow and protect the meter and backflow preventer from damage due to excessive flow. Series 994HMB meets AWWA C701 meter requirements and is ideal for use in existing hydrant meter hookups. Factory assembled and tested. Watts 994BLT is Less Meter.