A fiberglass Packaged Metering Manhole with a factory integrated Montana Flume. The Montana Flume has a offset discharge box to allow the flume to match up to the existing line configuration.  

When integrated into Packaged Metering Manholes, the Montana and HS/H-type flumes have their free-spilling discharges collected in discharge boxes.  Unlike other flume types, the flow out of these boxes doesn't have to leave on the same angle as the flow coming in.  This can make them more useful than other flume types so long as there is sufficient elevation to allow free-discharge out of the flume.