The Crystal Pro speaker kit comes with an industry leading 3 layer back wave dispersion pad, made from an aluminium foil which will properly disperse those unwanted back waves and won't hold water and rot like many other foam alternatives. The included closed cell foam rings come in a variety of sizes making them suitable for use in virtually any installation. Sealing drivers to door trims, spacers to door skins, holding tweeters in place, your imagination is the limit!