All agreements concluded outside of the WTO framework (and granting additional benefits beyond the WTO MFN level, but applicable only between the signatories and not to the rest of the WTO members) are called "preferential" by the WTO. According to WTO rules, these agreements are subject to certain requirements such as notification to the WTO and general reciprocity (the preferences should apply equally to each of the signatories of the agreement) where unilateral preferences (some of the signatories gain preferential access to the market of the other signatories, without lowering their own tariffs) are allowed only under exceptional circumstances and as temporary measure.