Features:

1.Adapts a 3.5 mm headphone plug for use with a  smaller 2.5 mm mini jack socket.Adapter Stereo 2.5mm (Male) Mini Jack to 3.5mm (Female) Jack Socket.This allow you to use your favorite 3.5mm earphone with some 2.5mm Mobile Phone.PDA, IPAQ, MP3 player or audio player device. 

2.2.5 mm male jack to a 3.5 mm female jack 

3.Converting "full size" jack plugs to audio equipment fitted with mini-jack sockets

4.Change some  MP4 , MP3 and CD player to use 3.5 mm earphone . 

5.Some  MP4 , MP3 and CD player is 2.5 mm plug , so this adapter is use for let them to use 3.5 mm earphone