VEHICLE COMPATIBILITY:for Buick LaCrosse 2005-2010for Buick Rainier 2004-2007for Chevrolet Silverado 1500 2002-2014for Chevrolet Silverado 1500 Classic 2007for Chevrolet Silverado 1500 HD 2002-2006for Chevrolet Silverado 1500 HD Classic 2007for Chevrolet Silverado 2500 2002-2004for Chevrolet Silverado 2500 HD 2002-2014for Chevrolet Silverado 2500 HD Classic 2007for Chevrolet Silverado 3500 2002-2006for Chevrolet Silverado 3500 Classic 2007for Chevrolet Silverado 3500 HD 2007-2014for Chevrolet SSR 2003-2006for Chevrolet Trailblazer 2002-2009for Chevrolet Trailblazer EXT 2002-2006for GMC Envoy 2002-2009for GMC Envoy XL 2002-2006for GMC Envoy XUV 2004-2005for GMC Sierra 1500 2002-2014for GMC Sierra 1500 Classic 2007for GMC Sierra 1500 HD 2002-2006for GMC Sierra 1500 HD Classic 2007for GMC Sierra 2500 2002-2004for GMC Sierra 2500 HD 2002-2014for GMC Sierra 2500 HD Classic 2007for GMC Sierra 3500 2002-2006for GMC Sierra 3500 Classic 2007for GMC Sierra 3500 HD 2007-2014PRODUCT INFORMATION:Material: Metal, PlasticColor: BlackVoltage: DC 12VTerminal: 4 BladesTerminal Gender: MalePERFORMANCE:OE NO. : 15016745/13506836Direct replace the old or broken headlamp relay.When you turn on your headlights, that switch activates a relay. That relay, in turn, actually provides the electrical connection between your headlight bulbs and the battery. Fuses are also involved in order to provide a sacrificial failure point to protect the rest of the wiring.