This is the EPOS Sennheiser D10, EPOS D10 II replacement (or extra) wireless headset or your exisitng EPOS D10 or D10 II system, including the USB model.  It does not include the D10 base. 

Key Features:

• Convertible Headset design (either over-the-ear, over-the-head) or behind the neck - optional
• EPOS ActiveGard technology protects users against  sudden sound burst in the line.
• Noise Canceling Microphone
• Up to three additional guests can join the same conference call
• Fast charging - re-charge 50% of the battery in 20 minutes.
• Compatible with Sennheisers HSL 10 II lifter or EHS cable (sold seperately)
• 1000577

For more details, see Sennheiser D10 Phone datasheet