Hattersley metering stations (such as their Fig. M2000 / M3000 / Fig. 1000 models) are compact, wafer-style flow measurement modules inserted into heating or cooling circuits; they incorporate a precision orifice and upstream/downstream test ports (often colour-coded) to allow differential pressure measurements for determining actual flow rates, typically over a pressure range of –10 °C to 120 °C and suitable pressures (e.g. PN16 / PN25) in stainless steel or DZR brass.