The gold-colored Interlok® Filler Ring fits into the top-most Interlok groove in your cockpit setup to provide a flat surface for placement of a non-Interlok-compatible stem. This could be the headset top cover (as supplied) or the top-most Interlok spacer in your spacer stack. It is not placed inside the headset. (Note that the Interlok Filler Ring is not necessary for placement of a non-Interlok stem with Interlok top covers or spacers.)
If you need a replacement Interlok® Filler Ring, head on over to our Headset Parts & Accessories page. You’ll find them under every series headset and in the “Solutions” section to boot.