3-PC. Fuel Tank Neck Adapter System Consisting of a Collar + Fuel Cap + Anti-Siphon. Designed to Stop Fuel Cap Leaks on Kenworth Trucks. Also Included is an Anti-Siphon Tube to Help Prevent Fuel Theft. NOTE: Sold Individually, Not as a Pair. If You Have Dual Tanks You Will Need To Purchase Two. The Leak Defender® + Anti Siphon is a 3-piece fuel tank adapter system, consisting of a collar, cap and Anti Siphon which creates a completely NEW sealing surface and replaces your old, worn fuel neck. And, yes, this will attach to a fuel neck where the threads are completely worn and fuel caps no longer seal. In fact, this is why we invented the product! These fuel cap replacements are for anyone who has ever had a problem with their current gas cap not sealing, or worse yet, leaking. The Leak Defender® collar attaches to and replaces your old, worn fuel neck. It has an o-ring underneath which seals to your existing fuel neck when tightened with a strap wrench and is securely fastened with set screws. It is sealed along the outer perimeter, away from the inner perimeter which is prone to wear and tear from everyday fueling. Our innovative fuel cap replacements will ensure a safe and tight seal on your gas tank, every time. It’s machined from billet aluminum allowing it to be made with a high degree of precision and with the strength to withstand the wear and tear of everyday fueling. Can your old, worn-out fuel neck say the same? Discover for yourself how our fuel cap replacements for Peterbilt, Kenworth, International, and more can give you the peace of mind that comes with knowing your gas tank will be sealed shut, no matter what.