I don't have a donut gasket and can confirm this. You've heard the sound clips. The bolts are tight enough, at least in my experience.Really? No donut gasket and no leak?? In my research theres no gasket used cat to b pipe, theres a metal ring in the pipe if you look at both ends and they say this is used as the gasket. So i have the donut but no cat to b pipe gasket. With my aftermarket piping i intend to add a gasket there.