Awesome Retro Accessory! All Metal High Quality Pressure Die Cast Gray Hammertone Finish Attaches To Any Vacuum Source On Non-Fuel Injected And Non- Computer Controlled Engines Mounting Instructions And Hardware Included The Original Hollywood Wolf Whistle is billed as a Blast From The Past and Built To Last, this intake horn produces the famous, sexy wolf call that always attracts attention from everyone. Simply attach it to a source of vacuum on a non-fuel injected or computer controlled engine and you are on your way to laughs and catcalls from your friends. NOTE: The brass insert that contains the whistle assembly can work itself loose and may fall out of the horn. To prevent this, we highly recommend that you remove the insert and apply an amount of clear silicone to the threads, install the brass insert and let it set overnight. This should prevent the insert from vibrating loose.