Overall Many phones and other digital devices today come with a 2.5mm headset plug, which will not allow a 3.5mm headset to be used. This 2.5mm female converter headphone audio extension cable allows you to use 2.5mm earphone headset on some 3.5mm Mobile Phone PDA, IPAQ, MP3, MP4 player or audio / video player device. Feature 1, Connector 1: 2.5mm TRRS Male 4-poles (tip, ring, ring, sleeve) 2, Connector 2:3.5mm TRRS female (1/8 inch) 3, 4 Poles stereo cable support mic/headphone Function 4, Adapter offers stereo / mono functions to convert 3.5mm audio 5, Gold plated connectors resist corrosion and the tarnish 6, Cable Length: about 20cm 3.5mm Plug Most computers and mobile devices use the 3.5 mm headset audio connection; Most music headphones and headsets are manufactured with a 3.5 mm connector. 2.5mm Jack 2.5 mm jack is approximalely 3/32 inch in diameter. The 2.5 mm jack is standard for telephones that support headsets, including oHice phones and some cordless phones. Most 2.5 mm headsets produce Mono, single sided, audio. Package 1x Gold Plated 2.5mm male to 3.5mm female stereo audio cable extension NOTE Since most 2.5mm devices are mono, you will only hear mono-channel sound in one (left) ear.