Radicals may be the ultimate track day car. They are light, powerful and have downforce! They range from 1300cc to 2600cc. They can be a one or two seater. Although they aren't built for a specific race series in a national organization, they sometimes can be found running in the unlimited class or with class designed cars (sports racers)where they manage to fit into the rulebook. You can find them running in NASA and SCCA, among others.
There is, of course, a series just for Radicals, the Radical Cup. Radical Cup West is a 10 event series running in the West on tracks like Spring Mountain, Laguna Seca, Thunderhill, Willow Springs, Miller and Buttonwillow.
Radicals have good support from Radical West, the USA West Coast distributor. Sales and service are excellent. They even have a home track in Nevada.