Karting is open-wheel racing in small four-wheeled karts, go-karts, or gearbox shifter karts, usually on scaled-down circuits, and is often a path into Ginetta Juniors, FIA Formula 4, FIA Formula 3, FIA Formula 2, and FIA Formula 1. Nico Rosberg, Ayrton Senna, Lewis Hamilton, and Michael Schumacher started in karting. Speeds vary; Super Karts can exceed 260 kilometres per hour (160 mph), while recreational karts for the public may be limited. Amusement park karts may use 4-stroke engines or electric motors. Racing karts use small 2-stroke or 4-stroke engines. Air-cooled industrial 4-stroke engines, sometimes lightly modified, make about 5 to 20 hp from Briggs & Stratton, Tecumseh, Kohler, Robin, and Honda for racing and fun karts. Stronger 4-stroke units from Yamaha, TKM, Swissauto, or Aixro (Wankel) make 15 hp up to 48 hp, run to and around 11,000 rpm, and are built for karting, including some National Championship classes like the two-strokes. Dedicated makers build 2-stroke kart engines, including WTP, Comer, IAME (Parilla, Komet, Woltjer), TM, Vortex, Titan, REFO, TKM, PRD, Yamaha, and Rotax.