My son just installed front speakers last night. Volvos are always a pain on the front speakers and he made spacers out of wood. The speakers were round and the door panels require that two sides are flat. so he made two round spacers and cut the two sides flat two fit the door panel. The other thing they have been doing is wrapping electrical tape around the outside of the spacer. Makes it look like the spacer is black plastic. My other son has had his on for two years and they still look like new!