The Leak Defender Fuel Cap Replacement O-Ring is a practical solution for heavy truck owners. Sold individually, this replacement O-ring fits most Leak Defender Fuel Caps. Heavy Truck Solutions recommends replacing the original O-ring or gasket every 3-5+ years. This product ensures a secure seal, preventing fuel leaks and potential hazards. Its practicality and durability make it a must-have for any heavy truck owner.