I used a CS-50 for years, until a combination of being worn out, and interference from wireless networks made its quality decline beyond use. I missed much the ability to use the headset throughout my office, with both hands free, and all of my resources available without laying down the phone or being bound by a wired headset's short cord. Finally broke down and replaced the CS-50 with the CS-55. Wish I'd done it months ago! Same reliable Plantronics quality, works with the HL-10 lifter that I already had, and is crystal clear with the Dect 6.0 technology. I've used several different headsets over time, and none beats the Plantronics!