Please don't waste your money on a "kit". All this is is a garage door seal you can pick up at stores like lows for $12. They even had the two types of material, one like rubber, one like foam. You will want to use screws as well as tape to keep it looking nice. I've got this on the front lip as well as down the side skirts on my Honda fit. If you wanted to do the side skirts I would suggest getting a door molding kit while you are at the hardware store. Just find one that is aluminum with the holes already drilled. Cut it to the side skirt length and pull out the rubber seal. Place the rubber "lip" between the side skirt and the aluminum strip and put the screws in.

The good thing about doing this is less air turbulence under the car (same as if you lowered it). It also has the look of lowering the car if you do the side skirts as well. It should also improve mileage by a very small amount because of the air flow under the car. It also helps in cross winds in my front wheel drive car.