Plantronics S8240-M: One Size Mono headset features noise-cancellation technology to keep your conversations clear even in noisy environments. Wireless DECT technology allows you to roam freely up to 590′ away. Multiple wearing styles ensure you have all-day comfort for everyone. Long-lasting battery provides up to 7 hours of talk time and up to 30 hours of standby. Call conference allows you to connect to up to four additional headsets (sold separately) for easy calls to one your teammates. Headset system sounds professional in any environment whether it’s connected to a desk phone, PC or mobile