It depends on the phone you want to use the earpiece with...Sony Ericsson HBH series of earpieces work very well with my Treo 650...I also tried earpieces from Motorola and Logitech with the Treo 650. The ones from Motorola had problems with answering and terminating calls using the earpiece button. Hanging up a call by pressing the earpiece button wouldn't actually end the call on the phone. However, these earpieces are popular and may work properly with other phones...The one from Logitech works well but tends to pinch your ear when wearing it. Its also a bit ugly...