Finally, in some countries the regulatory setting at national level defines the basic principles for the determination of tariff structures and levels, including the number of blocks, while leaving some degree of flexibility at local level so that local, technical and social conditions can be taken into consideration. This is, for instance, the case in Portugal (see Box 2.1). Italy is another example where general rules for pricing WSS are set but diversity in their application is significant. The fundamental difference with the Portuguese case is that tariff articulation is not regulated and supervised by a national regulator, but by local regulators at “Ambit” level.