Some cell phones, PDA"s and MP3 players use a 2.5mm headphone jack. Use this adapter to convert standard 3.5mm headphones to 2.5mm. Also useful when connecting your 2.5mm headphone jack on your cell phone or mp3 player to the AUX IN of your vehicle"s stereo, using a standard AUX-IN cable with 3.5mm male ends. Specifications/Features: Connector/Adapter Ends: Stereo mini female (3.5mm) / Stereo mini (2.5mm) male Gender 1: Female Gender 2: Male