3.5mm stereo plug to 2.5mm stereo jack adapter 3.5mm stereo plug to 2.5mm stereo jack converts 2.5mm stereo plug to a 3.5mm stereo plug.The adapter is assambled of black molded plastic with nickel-plated contacts.Black molded plastic construction nickel-plated contacts connector 1: 3.5mm stereo plug connector 2: 2.5mm stereo jack body diameter: 10mm