The rules for the use of Yokohama A021r tyres on racecars in production groups have been amended, please see

 http://www.segto.net/Wheels_Tyres_%20Brakes.pdf

    SEGTO is the governing body for the rules for the preparation and modification of race vehicles that are raced at all SEGTO affiliated club/race circuits. 

These rules enable any driver with a SEGTO race licence to race at any SEGTO affiliated club/race circuit. 

Each affiliated club/race circuit may also have extra rules and regulations that only apply to that particular club/race circuit.