The AP Exhaust 8991 connector is designed to make it easy to join two 4 inch exhaust pipes when one connection needs to slide over a pipe and the other needs to slide into a pipe. One end of this connector is 4 inch inside diameter, which slips over a 4 inch outside diameter exhaust pipe. The other end is 4 inch outside diameter, which slips into a 4 inch inside diameter pipe or muffler inlet. This makes it perfect for connecting a 4 inch exhaust pipe to a 4 inch muffler or component when the connection styles are different. Made from durable aluminized steel, it provides good resistance to heat and corrosion and can be welded or clamped for a secure, leak free joint. Ideal for exhaust repairs, custom builds, and performance upgrades. Please verify your pipe sizes before purchasing to ensure proper fit.