This gasket was developed to solve a problem customers where having with installation of the long tube headers on the 1GR-FE 4.0L V6 Toyota truck engine.
The flange and gasket recess size is different from the stock manifold and Y pipe and it is difficult to get a good seal and prevent the gasket from blowing out. After a few years of testing different solutions URD developed this gasket to solve the problem.
If you are installing Long Tube Headers or an aftermarket Y pipe on the 4.0L V6 you will need TWO of these gaskets.
If you use new or reuse stock type gaskets they will likely fail in a short period of time.
Note- If you purchase the Long Tube Headers or Y pipe from URD you have the option to purchase this gasket with headers or Y pipe at a significant discount.