Brake fluids for older cars and vintage cars are specially designed to be compatible with the materials used in vintage brake systems. Older vehicles often contain components such as natural rubber seals or certain metal alloys that can be damaged by the aggressive additives in modern fluids. The use of inappropriate fluid can lead to swelling and destruction of the seals, causing leaks and brake failure. Therefore, silicone-based or specific glycol fluids are often used for vintage cars. Silicone-based fluids have the advantage of being "hygroscopic", meaning they do not absorb airborne moisture. This protects the brake system from internal corrosion, which is a risk especially on vehicles that have been stationary for a long time. In addition, some vintage cars, typically French makes, require special mineral-based fluids that are not interchangeable with glycol or silicone fluids. The choice of the correct type of fluid is therefore dependent on the design and materials of the specific vehicle's braking system.