Fertan: HT Cavity Protection Wax offers exceptional protection against rust and corrosion in cavities and unseen areas of your vehicle. After application the product forms a transparent layer which is only dry on the surface repelling water away from metal surfaces. The layer of wax remains flexible for years. Any cracks that may normally appear due to flexing, close automatically to ensure optimum rust protection is preserved HT Cavity Protection Wax conforms to the highest current European specifications for both performance and environmental damage. Where cavities may be subject to existing rust (usually on non-new vehicles) de-rust with FERTAN before application. Ensure you observe the Fertan instructions of use and allow 48 hours before beginning wax treatment.