main thing is to help protest speakers from water. most of the time they only do a so-so job. they also choke bass out of a speaker. personaly i think they are a waste.
i added 6-1/2" in my doors on my yj about 5y ago and mine are still goin strong. at this point i got my money out of my speakers. if you have factory/aftermarket speakers and they are paper cone won't matter much anyway. if any water hits that cone it will start on it's way out. any poly speaker will be water resistent (not water proof). i just make sure i use dielectric grease on my connections...will help against rusting etc
95 YJ, 4" suspension lift, 32's, 2.5l 4 cyl (350 built and waiting to be installed in spring, along with ford 8.8 rear end)