Farmer j, you probably purchased the black $50spark arestor we sell, this is legal, if you look at the "locomotive and small engine spark arrestor guide , this tells you EVERY type of LEGAL arrestor, if it's in there its legal, and it also states , it is NOT a requirement to have USFS stamped on the arrestor, it is however a requirement to have the manufacturers name and or abbreviation and a model number that will crossover to the book, and that it does.