All 50 Class 4 - MX5 Road Cars - MX5 Mk1-Mk2.5 up to 2000cc 4 Class 4a - Road Cars - Series Production up to 1400cc 4 Class 4b - Road Cars - Series Production 1401-2000cc 7 Class 4c - Road Cars - Series Production over 2000cc 5 Class 4d - Road Cars - Specialist Production, any capacity 2 Class 5 - Modified Cars - Limited Production Marque Sports Cars up to 2000cc 0 Class 6 - Modified Cars - Limited Production Marque Sports Cars over 2000cc 0 Class 7 - Modified Cars - Series Production up to 1400cc 1 Class 8 - Modified Cars - Series Production over 1401-2000cc 2 Class 9 - Modified Cars - Series Production over 2000cc 2 Class 11 - Modified Cars - Specialist Production Cars, any capacity 2 Class 13 - Historically Interesting Cars, pre 1972, any capacity 3 Class 15a - Sports Libre Cars up to 1400cc 2 Class 15b - Sports Libre Cars 1401-2000cc 3 Class 16 - Sports Libre Cars over 2000cc 0 Class 17 - Racing Cars up to 500cc complying with the eligibility rules of the 500 Owners Association 1 Class 18 - Racing Cars up to 600cc 0 Class 19 - Racing Cars over 600 cc and up to 1100cc 11 Class 20 - Racing Cars over 1100cc and up to 1600cc 1 Class 20a - Formula Ford Racing Cars manufactured pre-1994, Kent Crossflow engines only. Pre-1994 rules apply 0 Class 20b - Racing Cars built up to 1985 0 Class 21a - Racing Cars over 1600cc and up to 2000cc (Normally Aspirated) 0 Class 21b - Racing Cars over 1600cc and up to 2000cc (Forced Induction) 0 Class 22 - Racing Cars over 2000cc 0