Item is a drivers door window express down module with PN 16603645 stamped on it. It is located at the bottom of the door. Some people wire them up so the passenger window also has the express down feature.  I have been told that the GM PN is 16627302 for the most recently updated version. PNs 16626271 and 16603645 will work as well. Do your own checking to make sure its the part you need.