The Dual Handsfree Stereo Adapter allows you to use your favorite set of 3.5mm headphones or earphones with your handheld! Additionally, with this adapter, you can enjoy easy handsfree communication with a single-touch answer call button and an integrated microphone. If you receive an incoming call while listening to music, you can answer your phone with one simple touch of a button, and the integrated microphone allows you to talk handsfree. 2.5mm stereo plug (male) to 3.5mm. Dual Handsfree Stereo Adapter for Sony Ericsson Mobile Phones Sony Ericsson k750, W550, W800 and W900