All of our racks require a 2" hitch. Larger hitches can be stepped down using adapters. Hitches smaller than 2" are not recommended. Required hitch class depends on what rack you want to run. For off-road driving class 3 or higher is recommended.
Tongue weight (TW) is not always a correct representation when deciding how heavy a bike rack and bike combo your hitch can support, as generally this is more related to the towing capacity of the vehicle than the strength of the hitch. Rated tongue weight is usually around 10% of towing capacity.
Not all hitches are created equal so if in doubt it's best to consult with the hitch manufacturer.