Universal fits for most cars w/OEM Muffler Exhaust Size: S,M,L,XL Size: S,Tail Pipe diameter : 32-43mm,Length: 11cm,Displacement : 1000-1600cc Size: M,Tail Pipe diameter :37-48mm,Length: 11cm,Displacement: 1600-2000cc Size:L,Tail Pipe diameter :44-55mm ,Length:11cm,Displacement :2000-2400cc Size:XL,Tail Pipe diameter:56-85mm,Length: 12cm,Displacement: 2400+cc 1" muffler tip for best effect (OEM Muffler) Install on Aftermarket muffler, Catback, Axleback muffler it will not produce any sound. Installation: Loosen the screw on the Turbo Sound Whistle,Place the Turbo Sound Whistle body inside the exhaust muffler with the larger opening facing the inside of the muffler Screw,the screws on the Turbo Sound Whistle to tighten the item,so it doesn't fall off while driving Package includes: 8 x Turbo Sound Simulator Whistle