Competition Class in the

The main championship consists of capacity classes open to all machinery with two or sometimes three wheels

The competition classes are:
100-250cc (Green plate, White numbers)
250-350cc (Blue plate, White Numbers)
350-500cc (Yellow plate, Black numbers)
500-750cc (White plate, Black numbers)
750-1300cc (Red plate, White numbers)

Additionally there is the Sidecar/Trike competition class:
One Wheel Drive (White plate, Black numbers)
Two Wheel Drive three track (White plate, Black numbers)

The details given on this page are all Tigger's fault and have sod all to do with the NHCA - officially