This is the Jeep tail light connector found on very early Jeeps as well as Dodge GMC and other early series WWII Trucks also see Dodge / Motorcycle Listing). This connector is the type that fits into the tail light fitting rather than over the outside which is the more common fitting used on general WWII production.  This kit now includes the Rubber Tail Light Insulator Plug.  This Insulator Plug is also available separately.