I use this headset on my Panasonic cordless phone. It works better than the Panasonic headset I had purchased. (2.5mm)Also, I use the cellet 3.5mm on my blackberry where it works very well. These have four conductors (metal rings), and are harder to find. Perhaps they are being discontinued because they are selling for under $7, yet they are better than those priced much higher.All the headsets I have tried eventually break. One reason my be accidentally yanking on the cord over time. The other problem is that eventually, from three to nine months the microphone stops working. I suspect it might be static electricity. This happens across brands. Perhaps they have fixed it by now.Something Star brand headsets I bought at Radio Shack always failed this way. They had a warranty so I would always just return the headset for a new one. Radio Shack doesn't carry them anymore and their warranty is more limited on what they have. You just don't get an immediate exchange at the store. You have to mail it in.