No word from the OP in more than two months. Hope the Ultraseal didn't destroy his car.
Ride-On vs Ultraseal: Reading the description, they sound like very similar products. Ultraseal's smallest container seems to be one gallon for 57.50, and that should be enough to do eight tires.
Ride-On is available in convenient 16 Ounce cans (bottles) each sufficient for one tire. A kit of four bottles costs 54.99.
Shipping not included: Looks like Ultraseal is about half the price per tire, and would be more economical,
IF you've got a couple vehicles you want to treat.
A one vehicle person, like myself, would be better off with the Ride-On, assuming equivalent products. And, they appear to be.