Class
CATEGORY 1 = Registered before 31.12.67    
B1 = Cars up to 1000cc    
B2 = Cars up to 1300cc    
B3 = Cars 1301cc to 1600cc excluding Twin Cam engined cars    
B4 = Cars 1601cc to 2000cc including Twin Cam engined Cars    
B5 = Cars over 2000cc including all Porsche 911s    
CATEGORY 2 = Registered between 01.01.68 and 31.12.74    
C1 = Cars up to 1300cc    
C2 = Cars up to 1600cc including 2 Valve Twin Cam engined cars    
C3 = Cars 1601cc to 2000cc    
C4 = Cars over 2000cc    
C5 = Cars Over 2000cc including All Multi Valve Twin Cam engined cars    
CATERGORY 3 = Registered between 01.01.75 and 31.12.81    
D1 = Cars up to 1300cc    
D2 = Cars up to 1600cc including 2 Valve Tqin Cam engines    
D3 = Cars 1601cc to 2000cc    
D4 = Cars over 2000cc including Multi Valve Twin Cam engined cars    
D5 = All othe Multi Valve Twin Cam engned cars    
CATERGORY 4A = Registered between 01.01.82 and 31.12.85    
E1 = Cars up to 1600cc    
E2 = Cars over 1601cc    
CATEGORY 4B = Registered between 01.01.86 and 31.2.90    
F1 = Cars up to 1600cc    
F2 = Cars over 1601cc    
CATEGORY K = FIA Appendix K cars Registered before 31.12.85    
G1 = Cars up to 1600cc    
G2 = Cars over 1601cc    
SAFARI = Safari Vehicle Specification up to 31.12.85    
H1 = Cars up to 1600cc    
H2 = Cars over 1601cc    
OPEN = Roger Albert Clark Open Rally    
J1 = Cars up to 1000cc    
J2 = Cars 1001cc to 1400cc    
J3 = Cars 1401cc to 1600cc    
J4 = Cars 1601cc to 2000cc    
J5 = Cars over 2000cc    

Class
CLASS B = Historic Vehicles Registered before 31.12.67    
CLASS C = Historic Vehicles Registered between 01.01.68 and 31.12.74    
CLASS D = Historic Vehicles Registered between 01.01.75 and 31.12.81    
CLASS E = Historic Vehicles Registered between 01.01.82 and 31.12.85    
= Historic Vehicles Registered between 01.01.86 and 31.2.90    
CLASS F = Historic FIA Appendix K cars Registered before 31.12.85    
2WD = Complying to 2019 Motorsport UK Technical Regulations    
CLASS G = Cars up to 1000cc    
CLASS H = Cars 1001cc to 1400cc    
CLASS I = Cars 1401cc to 1600cc    
CLASS J = Cars 1601cc to 2000cc    
CLASS K = Cars over 2000cc