The AP Exhaust 9333 reducer coupler is designed to connect a 3.5 inch exhaust component to a 3 inch exhaust pipe. One end of this coupler is 3.5 inch outside diameter, which is made to slip into a 3.5 inch inside diameter pipe, muffler, or other exhaust component. The other end is 3 inch inside diameter, which is made to slip over 3 inch outside diameter exhaust tubing. This is a great solution when you need to step down from a 3.5 inch ID connection to 3 inch tubing in a clean, secure way. The smooth tapered design helps maintain proper exhaust flow and reduce turbulence between sizes. Made from durable aluminized steel, it provides good resistance to heat and corrosion and can be welded or clamped for a strong, leak free joint. Please verify your pipe sizes before purchasing to ensure proper fit.