Ubiquiti have changed the name of a few of the NanoBeam devices to PowerBeam the units are the some the only differance is the name and part number.

NBE-M2-400 - Changed to PBE-M2-400 now part of the PowerBeam Range

NBE-M5-300 - Changed to PBE-M5-300 now part of the PowerBeam Range

NBE-M5-400 - Changed to PBE-M5-400 now part of the PowerBeam Range

NBE-M5AC-500 - Changed to PBE-5AC-500 now part of the PowerBeam Range
The Ubiquiti PowerBean is a High-Performance airMAX® Bridge PTP or PTMP 
Models: PBE-5AC-500, PBE-M5-400, PBE-M5-300, PBE-M2-400
Uniform Beamwidth Maximizes Noise Immunity
Innovative Mechanical Design
High-Speed Processor for Superior Performance
Scalability High capacity and scalability.
Long Distance Capable of high-speed, carrier-class links.