I recently installed some of these products on my hhr's rear hatch lift gate and the panels that let you access the tail lamp bulbs. I must say, im quite impressed with the amount of rattles that have dissappeared, i also noticed my exhaust isn't as loud in the cabin anymore. The bass sounds more crisp and clear with no rattling, i must say that i recommend doing this to anyone's hhr who is looking for some nice quality bass, not to mention im gonna need it with the addition of my jl audio 10w6v2 subwoofer thats going to be installed shortly. Has anyone already installed these products on their hhr's, im curious to see the results of other peoples install's.