I ordered this to install a Flowmaster Super 44 on my truck and it fits perfectly. This was the only place I could find the right size adapter as all the dealerships around me (Autozone and Advanced Auto Parts) didn't have adapters that size. There are no issues with him, he is still going strong and showing absolutely no signs that anything is wrong with him. Both the inlet and outlet were perfectly round, allowing it to slide easily through the tubes. Good product! EDIT: This adapter is 2.5"…