Various upgraded features, including a Copeland® scroll compressor, a variable-speed fan, rifled condenser tubing, and a subcooling coil, make Mueller® E-Star® OE condensing units the most energy-efficient and cost-effective refrigeration system. The user-friendly design of Mueller E-Star OE units lets you access electrical controls and valves with ease. An oil sight glass and fill port allows you to monitor and change refrigerant oil and meet future refrigerant requirements. Mueller condensing units outperform all refrigeration units regarding reliability, efficiency, and value.