Nokia HS-40 2.5mm Mono Headset for Signature - Original OEM - Non-Retail Packaging - Black The lightweight and compact design ensures portability and maximizes comfort. To keep you connected hands free whenever the need arises. This HS-40 mono headset from Nokia features an inline microphone as well as answer/end buttons for easy call management. This HS-40 mono Nokia headset is all business. Its business.