Tariff-rate quotas (TRQs) apply to imports of goods and are almost exclusive to agricultural goods. TRQs limit the amount of certain goods that may be imported into a country at reduced or zero rates of Customs Duty over a specified period of time. The limit may be expressed in units of weight, volume, quantity or value. Quantities exceeding the quota are subject to a higher duty rate. TRQs protect domestic producers from having to face competition from large quantities of imports, however they also allow exporters some access to the market.