Having tried four different types of 42mm crush gaskets, we found the best option is 42mm copper crush gaskets from Delkevic (pictured in a couple places on this thread). The 42mm gaskets are not on Delk’s website and they do not sell them on ebay. I only learned of them because I was on the phone with Matt at Delk to order the 41mm gaskets they recommend for VFR800s (Hoping the 41mm gaskets would crush to a functional size) and Matt said they have and sell 42mm gaskets. The 42mm gaskets from Delk have a skinny, round cross section and crush to a perfect id that is larger than the VFR’s exhaust port. The Delk gaskets have a seam on one side - we put the seam side down, toward the head, to give the header’s collar a cleaner surface to press against. They create a good seal. All the other 42mm gaskets we tried were too big to fit into the head’s sleeve - where the headers seat - without grinding and/or cutting. I’m editing out reams of trial and error, grinding, cutting, splicing, and cursing data. Even the Delk washers are difficult to get started into the sleeve, but because they are so thin, they can be persuaded past the lip of the sleeve. After starting the gaskets in by hand, the headers do the rest of the job of escorting the gaskets into their final resting place, then crushing them. It’s a lovely kind of slow-paced violence.