These “Green Label” discharge mufflers are uniquely designed for the higher pressure requirements for systems using R-410A. The tough requirements needed for these special models are made to the approved Underwriters Laboratory requirements necessary to meet the 675 p.s.ig. working pressure. *Models MH-30, MH-60, MH-80 and MH-110 require pressure relief valve (not supplied). The chart below shows the models available.