The headset Discovery 665 has:AudioIQ™ ; intelligent audio processing (exclusive Plantronics). DSP (Digital Signal Processing). 3.5 hours of talk time and 80 hours of standby. weights only 9 grams. Case with led - call indicator.
The headset Discovery 650 has:
Multi point technology that allows the connections of more than one Bluetooth device simultaneously 5 hours of talk time and 150 hours of standby, with the AAA battery charging pocket weights only 9 grams Charging pocket with vibration alarm