The older speed carbs had speed writen on the side of the carb. The new speed carb doesent have speed on them, and hate to say the ideal screw hardley works on the nw speed carb, but they come with a nice big o-ring, works good. My friend didnt like the new speed carb, he used his same slide, that was on hia old speed carb, anyway lost 8 mph, hes bull headed wont change slides, thinks it a junk carb, hes going to put his old one back onl hes got a pice broke where he screws the boult on to hold his air filter on, hes bull headed and no patichence