Side skirts are a part of body kits or ground effects kits that adds onto the side of the vehicle usually to the rocker panel or into the door jam to lower the vehicle profile to match the lower front and rear bumpers. Side skirts are manufactured in 3 primary materials FRP (fiberglass reinforced plastic), Polyurethane and carbon fiber. FRP side skirts are most common due to the low cost of manufacturing thus having the largest selection. These side skirts are light weight and affordable but they are susceptible to cracking if you bottom out hard or run into a curb. One of the good things about FRP is that it is the most customizable and repairable of any materials used for aerodynamics. Polyurethane products are extremely expensive to manufacture but offer the most flexibility and durability on street driven vehicles. The down side to polyurethane is that it is very heavy and due to costs has a much smaller selection available. Carbon fiber side skirts are extremely light weight and most commonly used in motorsports as well as in the custom car show culture. When purchasing aftermarket side skirts please be advised that it will require professional installation as custom parts follow a different process than OEM parts. Always consult with a shop that has experience with body kits and custom vehicles to get the best results!