Napa Rust Proofing Wax Oil - Black - 1L Schutz - Vehicle Cavity Sealer. This product is a wax oil designed for rust proofing and cavity sealing in vehicles. Always check this product is correct for your vehicle before purchase. UK EBAY SELLER SINCE 2010. Dedicated to customer satisfaction with great feedback. Over 10 years of experience in the automotive business. Free expert advice available. Genuine UK stock, all shipped from the UK. No leak guarantee, any damages will be replaced. Free UK Mainland Shipping on all listings. Express Shipping Available. 60 Day Returns policy. Brand: NAPA. Quantity: 1 Unit.