This frangible coupling is used on some manufacturers' elevated airfield lights to avoid replacing 2-inch hub baseplates or stakes when retro-fitting. Other solutions involve a threaded reducer as a separate part, which we believe is cumbersome and rather expensive. Our couplings are sourced from an FAA Certified manufacturer and come complete with a stainless-steel lock screw. If your lights have this coupling, we recommend that you always have a few on hand. THE USE OF AN ANTI-SEIZE COMPOUND ON THE THREADS WHEN INSTALLING IS STRONGLY RECOMMENDED. Such compound is usually available locally through an auto parts supplier.