EXEDY USA breaks all events into a two tier system.
Tier 1 – National Events. Events in tier one have huge turn outs and/or have a national footprint. These are national events with the highest competition. Usually Tier one events are part of a series such as Formula Drift.
Tier 2 – Regional Events. Events in tier two are local or regional and have high competition. Usually Tier two events are part of a small regional series or a traveling sanctioning body such as NASA. (there are a couple exceptions to this).