Legal essentially everywhere, but it MUST carry a marine standard.
This is one body's answer, not the sport's. You are bound
by whichever body sanctions the event you enter, and where both govern you,
you are held to the stricter of the two. The differences are set out in
the rulebook comparison.
Publish the certification on the product page. An uncertified filter fails tech in every class.
Where it stands, class by class
20 classes, grouped by the answer rather than listed one by
one, because an answer that holds for a class usually holds for every class
that borrows its rules.
Legal 20 classes
Must meet USCG, SAE J-1928 Marine or UL-1111 Marine backfire flame arrester standards.
Aftermarket flame arrester: if the rule your class applies reads
differently to you, or the rulebook has changed since this was read, ask.
We answer with the section we read it from, or that we have not read it.
Ask a rules question.