With most vehicles --- if you don't get a trim ring / installation kit then you may have a gap around the outside of your aftermarket head unit. Looks bad, easier to steal.
For less than $10 for most vehicles, if you require one, I would highly suggest it. As well as a wiring harness, no questions asked.
uhh its a 96 Tl. The factory hu is one of those big ones that take up a lot of space. Once i take it out will the installation kit have the stuff to fill up that space?