The Leak Defender (A 2-Piece Fuel Neck Attachment System), Collar & Cap, Creates a NEW Sealing Surface & Stops Leaking Fuel Cap Issues on Freightliners! Also Included is an Anti-Siphon. (Patent Pending). Purchase here: /products/leak-defender-for-freightliners/ Stop Leaking Fuel Caps Save on Repair Costs No Downtime Stay DOT-Complaint Stop Diesel Fuel Theft 100% Money Back GuaranteeThe Leak Defender is more then just a shiny new cap. . ..it is a 2-piece system consisting of a collar and cap which creates a completely new sealing surface. The Leak Defender Collar attaches to your existing fuel neck, sealing along the outer perimeter, away from the inner perimeter which is prone to nicks and abrasions. The Leak Defender Cap attaches to the collar and is made with the same billet aluminum to withstand the wear and tear of everyday fueling. Also included is an anti-siphon device to prevent diesel fuel theft. NOTE: If you have dual tanks, you will need to purchase 2.