Made of ballistic nylon. Won't damage the vehicle. Perfect for small to medium size vehicles. Inflates easily and quickly. Extremely durable. Slides easily over weather stripping The Air Jack from Access Tools is the industry's best. The bladder is made out of ballistic nylon, not rubber, which is important because rubber stretches, while the nylon won't. The Air Wedge is meant for smaller vehicles. To further aid insertion, there is a built in stiffener that prevents the wedge from bending when you insert it.