Right now I have mine resting on top of the covers since it ddidn't come with them either. But most tweeters you buy will have the flush mount cups with them, you just need to use a Dremel or small hole saw to cut out an opening for the cups. You get the covers or factorys tweeters out but just sliding a small flat head screw driver under the edge and prying it up. As to if they do anything, YES most silk domes and related tweeters fill in the void above about 2K, that's where you get that crisp snap from say a cymbal or like instrument. Of course they will only work as good as the signal coming to them, most have a built in passive crossover to proitect them from lower freq's. Also, most of them are at such a high impedance that you can add them to your existing setup without having to worry about frying your head unit/amp. Hope all of this helps..........