Mueller W01073 2 1 8 x 1 5 8 Coupling The Honeywell 221729A Dust Cover The Honeywell 221729A Dust Cover is a professional grade protective housing designed specifically for the 7800 Series Relay Modules this brown coded compression spring ensures the necessary return force to maintain accurate proportional control in steam or hot and cold liquid systems 22 compliant fitting facilitates a precise reduction from a 2 1 8" OD (2" nominal) line to a 1 5 8" OD (1 1 2" nominal) line The Mueller Streamline W01073 2 1 8 x 1 5 8 Copper CxC Coupling is a high performance wrot copper reducing coupling engineered specifically for technical HVACR piping and pressurized supply lines