I've been using Zaino Z-16 Perfect Tire Gloss for some time, but heard so much about 303 that I ordered a gallon. Honestly, when I looked at both products, I thought they were the same thing, both a milky white liquid. After quite a bit of use though, I've determined that the Z-16 works better on tires and outside vinyl trim (looks better, lasts much longer, covers minor imperfections better). The 303, however, really made the rubber around the windows look great and the plastic and vinyl inside look fantastic. The Prelude had black plastic/vinyl trim inside, including the dash and door panels that were so sun damaged that I thought they were never gonna look good. 303 did the trick without the greasy, sticky look of Armor All and I was able to use several applications to get the final look I wanted. The Z-16 on the interior parts just seemed to go away and several applications didn't make any difference. Now I'm hooked on both the 303 and Z-16! Just gotta use it for the right things, I guess. Just as a side note, I did outside vinyl bumper strips, black plastic door handles and bumpers on my Cherokee with 303 on the driver's side and Z-16 on the passenger side. It rained a bit during the night and when I went out in the morning, the protectant on both sides of the car had run and streaked so badly that it looked like Mimi (from Drew Carey's shoe)mascara after a good cry! It all cleaned up with Zaino Z-6 QD with no problem but it was kind of a shocker since I had never had it rain on the protectant before.