In general, to be called a hotel, an establishment must have a minimum of six letting bedrooms, at least three of which must have attached (ensuite) private bathroom facilities. Although hotels are classified into 'Star categories (1-Star to 5-Star), there is no standard method of assigning these ratings, and compliance with customary requirements is voluntary. A US hotel with a certain rating, for example, is may look very different from a European or Asian hotel with the same rating, and would provide a different level of amenities, range of facilities, and quality of service.