I didn't use these in my car, because I had enough crap to cable tie onto, but when building PC's and trying to make em look good, these things work really really well. I know you can usually get about 1/2" or a bit more of wire in there if you smash it a bit. Very sticky 3M adhesion stuff on the back. They only stick once. They work really well in computer cases that are shiny aluminium, and on walls that are drywalled. Everywhere!!! You can get a pack of 10 at radioshack for $3.49.
