MUST PURCHASE TWO PIECES - FOR LEFT AND RIGHT. Add two to cart, the one model fits both sides. These custom-modeled pieces replace the metal earphone jack supports/liners that are too narrow to fit upgrade cable plugs, letting you use your Meze 99 Classics with Double Helix Cables or any other cable featuring the Eidolic Universal 3.5mm Jack. It is a very easy 5 minute installation with a small Philips screwdriver. For more details, photos, and how to install, visit the mods section of the Double Helix Cables website. Plastic is initially available and works great at a low cost; more materials will be tested by us and made available when they are confirmed as a perfect fit.