1-Usually used to connect a headphone out to another jack input
2-Plug your MP3 player to your in-car Aux port to listen to you favourite songs through your car stereo
3-Male Stereo 3.5mm Jack to Male Stereo 3.5mm Jack.
4-Also quite often used in connecting PC´s audio out/speaker out to the speakers on the side of monitors.
5-Also see the above image showing the Package contents
We have many items of different lengths

40cm 3.5mm 3.5 to Jack Audio Headphone Lead Cable product offered by Shenzhen Sosound Technology Co., Limited