KA2766 / KA2766 - Application Notes STILLEN all urethane ground effects. Our all urethane ground effects (front spoilers, side skirt and rear valances) are designed to enhance the shape of your SUV, truck, van and add aerodynamic performance. We offer a variety of designs for each component so you may mix and match to create a unique look. It's dramatic, detailed and adds the final touch to your personalized roller. All pieces are available separately. Limited Lifetime Warranty.