Hello Robert. The CIPA # 10202 mirror is not confirmed to fit the 2007 GMC Sierra Classic. The # 10202 is only for older models of this truck, which will explain why it is not fitting. Instead you will want the CIPA Custom Towing Mirrors # CM10800 which comes with the left and right side towing mirrors for a 2007 GMC Sierra Classic. Our install video is linked below. view full answer...