250cc which stand for 250 cubic centimeters, is a common engine size for motorcycles. For years it was the standard size of all motocross and Supercross races and the different series were referred to by size(i.e. "the 250 class"). Recently, those at the normally 250cc level have switched to riding with four-stroke 450cc engines. This has led to a name change and the series is now called simply the "Supercross Series" rather than the "250cc Supercross Series." Technically, 250cc engines are still allowed in the Series, but they would have to be two-stroke engines, and so no one ever uses them. Now, what would normally be the "125cc class," uses four-stroke 250cc engines and has been renamed the "Supercross Lites Series."