If you need to add a panel-mount connection for telephone-interfacing projects but don't have the time or ability to cut a custom oval or square hole, this RJ-12 or RJ-11 Telephone Round Panel Mount Plug is the easiest and fastest way to panel-ify your existing phone kit. It's about 30mm in diameter so that you can drill a hole in your wood, plastic or metal with a common hole-saw or bit, no special shapes or filing required. Unscrew the plastic nut, insert the plug, and re-attach. Ta-da: Now you have a pass-through RJ-12 jack.