If you go NHRA.com, mouse over to rules, scroll down the list to "accepted oil retention devices", click, and download the list, you'll find a list of all currently accepted diapers and the classes that require what.....I'm sure the rule states "NHRA accepted oil retention device mandatory" in Supergas, Supercomp, & advanced et. It doesn't say SFI approved just NHRA accepted. The list says the same.