COMPATIBILITY: The module compatible with 2003-2007 chevy silverado; 2003-2007 gmc sierra 1500, 2500, 3500, 2004-2006 cadillac escalade, 2003-2006 escalade ext; 2003-2007 GMT 800 trucks; 2004-2006 yukon; 2004-2006 tahoe; 2003-2006 avalanche 1500. FUNCTION: This 6 high mod allows your low beams, high beams and fog lights to be on Simultaneously when turn on high beams. Note: low-beams and fog lamps will function normally when the high-beams are not turned on. EASY TO INSTALL: No modification needed, it took less than 5 minutes to install and works. Just find your fuse box, pull out 3 relays labeled Hdlp-Hi, Hdlp-Low, Fog Lp. Lay down the circuit board and reinstall these relays back into original position. MATERIAL:The circuit board is made of FR-4 PCB materials, sturdy structure is safer to use, durable and well worth. PACKAGE INCLUDED:1 PC Light Module 6 High Mod. COMPATIBILITY: Light Module 6 High Mod for Gm Compatible With Gmc Chevy Silverado Sierra 1500 2500 3500 Classic 2003-2007 Fog Lights Low Beams And High Beams Lamp On Simultaneously