Product parameters 100% new state Material: Made of 6061 T-6 aluminum processed by lightweight aluminum CNC Color: Black, blue, silver, Yellow, red (5 colors) Quantity: 1 Size: S, M, L, XL Diameter: about 2 cm Features: It is made of 6061 T-6 aluminum processed by lightweight aluminum CNC 1 inch muffler tip for best effect (OEM muffler) Installed on the aftermarket muffler, Catback, Axleback muffler will not produce any sound Simple and easy to install Gm is suitable for most cars with OEM muffler straight exhaust rather than elbow. Installation: 1. Unscrew the Turbo Sound Whistle 2. Put the main body of the Turbo Sound Whistle inside the exhaust muffler, the largest opening inside the muffler 3. Screw into a Turbo Sound Whistle to tighten items so they do not drop while driving Note: The sound level varies by size. The higher the number, the louder the sound. It is best to confirm the inner diameter of the exhaust port before purchase. If the whistle diameter is greater than or equal to the inside diameter of the exhaust pipe after 1CM extension, it will not be installed. Also, keep in mind that the volume of sound is related to the tailpipe propulsion and personal perception. After installation, the sound felt too loud or too small can not be used as a product quality problem. Individual models may have less propulsion or modified taildrum. Low or no sound, this situation cannot be used as a quality problem, please note! For small displacement of the vehicle, please choose large and large, you can choose small, because the principle of the whistle is air flow, large displacement, the bigger the whistle, the easier the sound. Note: For different car sizes, please check the size Size S suitable for: Liner diameter: 32-43mm Capacity: 1000-1600 cc Size M: Liner diameter: 37-48mm Capacity: 1600-2000 cc L size: Liner diameter: 44-55mm Capacity: 2000-2400 cc XL size for: Liner diameter: 56-85mm Displacement: 2400CC +