Don't even try to use Fel-Pro gaskets or aftermarket o-rings because as far as I can tell none of them will fit. Toyota products are my only viable option. This is a very specific shape and size for the 2004-2009 2nd generation Toyota Prius. I wish there was another way. I suppose you could just hook up the flex pipe, but you really need the spring bolts to create the long lasting vibration and wear they create on the manifold and surrounding pipes. In terms of cost, this is the cheapest genuine Toyota gasket I can find. Be sure to replace the manifold gasket with the catalytic converter as it will not fit onto any of the other flanges.