Features:

•  Autoscan on all receivers for simple and secure frequency selection
• 1440 frequencies within a 36MHz switching bandwidth for greater tuning flexibility
• Robust metal construction for durability
• Smaller bodypack transmitters and receivers(30% smaller than current EW)
• Pilot tone squelch(defeatable for backwards compatibility with original EW systems) 
• New battery concept(AA cells and rechargeable battery accessories)
• Transmitter battery status telemetry on all models
• Audio signal metering on transmitter LCD display
• External charging contacts on 300 and 500 series bodypacks
• XLR jacks on all rack-mountable units(including 100 series)

What does B Stock Mean?

Anytime a item is returned to a store, for whatever reason, it is sent back to the manufacturer. The manufacturer then tests the unit to find out if anything is wrong with it. If they find something wrong, they fix it. Most of the items sent back usually have nothing wrong with them. People return things because they changed their mind, buyers remorse, a host of reasons. The thing is, Sennheiser has the cleanest B stock we have ever seen and they back the warranty for the full 2 years just like the brand new units. The only thing you do not get is the box that you throw away after taking the headphones out of them, and maybe the manual which you can download from the manufacturer`s website. This is a great way to save money on some excellent Sennheiser product. Just think, these headphones have been tested and work fine. The new ones out there could be DOA out of the box.