*DISCONTINUED* by Plantronics.  No longer available. 

This is the Plantronics S11 replacement/spare headset. This headset plugs directly into Plantronics S11 base with modular (square) RJ-9 plug. This headset is the replacement for your existing S11 system only. It will NOT work with any other Plantronics amplifier.

If you wish to have a different headset for the S11 (ie. binaural headset), you can use any Plantronics H-series headsets  + Plantronics U10P cable