This simple adapter is designed to be used with our D14 headlight wiring harness (DNL.WHS.26000) to enable universal installation on any motorcycle with an H4 headlight. The H4 connecter plugs into your motorcycle to pick up the high and low beam signal and uses the D14 relay harness to pull the power from your batter ensuring that you can run the full destroyer beam intensity without overloading your factory headlight circuit. This adapter is necessary when installing the D14 Street Glide kit (DNL.D14.10100.K) on model years 2014 and older.