Poly CS540 DECT 1920-1930 MHz Headset Convertible Multi Pack (3 Pieces) - Mono - Wireless - DECT - 393.7 ft (120 m) - 20 Hz to 6.80 kHz - Over-the-head, Over-the-ear - Monaural - Ear-cup - Noise Cancelling Microphone - Black

Poly CS540A Headset with handset lifter TAA - Mono - Wireless - DECT - 393.7 ft (120 m) - Over-the-ear - Monaural - In-ear - Noise Cancelling Microphone - Noise Canceling - Black

Poly CS540A DECT 1920-1930 MHz Headset TAA - Mono - Wireless - DECT 6.0 - 393.7 ft (120 m) - Over-the-ear, Over-the-head - Monaural - In-ear - Noise Cancelling Microphone - Noise Canceling - Black