3.5mm FEMALE to 2.5mm MALE adapter: Stereo adapter 3.5 to 2.5 adapter is an audio headphone adapter and converter that adapts or converts 3.5mm headsets to a 2.5mm headset. Adapt larger 3.5 mm output of some audio headsets and other electronic music devices that you can plug into standard 2.5 mm headset opening of cell phones, etc. as an input jack using this 3.5mm to 2.5mm audio connector. This 3.5 millimeter to 2.5 millimeter pin connector has 2.5mm pin on one end and a socket to fit any 3.5mm pin from a typical headphone used with stereos, walkmans, or most MP3 player's headset openings. 3.5mm to 2.5mm jack adapter for less! 3.5mm to 2.5 adapter headset jack (or 3.5 to 2.5 adapter) is useful because majority of headsets available for most electronics like portable stereos, portable MP3 players, and walkman's have a 3.5mm pin that does not fit into majority of cellular phones that have a standard 2.5mm headset jack opening instead of the standard 3.5mm jack found on most portable radio, stereos, MP3 players, etc. 3.5mm to 2.5mm adaptor allows you to plug standard 3.5 mm stereo headphones into the smaller 2.5mm input available on most mobile phones.