Amazon.com: Vixen Horns 1/4" NPT Male to 1/2" NPT Female Brass Thread Expander Fitting for Train/Air Horn Tanks - Bundle of two fittings VXA1412-2 : Automotive
Amazon.com: Kleinn Air Horns 330 Roof Mounted Horn Fitting and Hardware Kit : Automotive
Air Horns & Accessories: AnythingTruck.com, Truck & Trailer Parts and Accessories Warehouse
Amazon.com: Vixen Horns 1/4" NPT (Male) Compression Fitting for 3/8" OD tubes for Train/Air Horn Tanks VXA7714 : Automotive
Amazon.com: Vixen Horns 1/4" NPT (Male) Compression Fitting for 3/8" OD tubes for Train/Air Horn Tanks - Bundle of four fittings VXA7714-4 : Automotive
Amazon.com: Hadley Horns H11477S Mounting Elbow and Tension : Automotive
Diagram of Parts of an Air Horn - Adjustable and Non-Adjustable - Air Horns by Grover
Kleinn Air Horn Juice - Worlds Best Thread Sealant - Kleinn Automotive Accessories