Grand-Am has only one class for Grand Touring cars which allows production-based GT racers at a spec somewhere between FIA GT2 and GT3 in terms of modification (e.g. the Porsche 911 GT3 Cup) to compete with purpose-built tube-frame "silhouette" machines reminiscent of the former IMSA GTO/GTU classes. Grand-Am also runs various under-classes more reminiscent of GT4, though closer to factory cars. For 2012, GT3 cars will be allowed, with spec wings and splitters, as long as they pass a test at the NASCAR Research and Development Center in Concord, North Carolina, thus allowing GT3 cars to run with few modifications relative to other series (NASCAR, the parent company of Grand-Am, does not permit anti-lock brakes or traction control to be used on Grand-Am GT cars).