Key Features: Mfr. Part #: 86179-01 or HP 85T27AA#ABA CS540 Spare Convertible Headset 7 Hours of Talk Time Noise Canceling Microphone DECT 6.0 Headset can be worn Over the Ear or Over the Head Compatible with the Plantronics CS540 Headset Package Includes: Headset Foam Ear Cover Battery