Usually HF filters are designed using inductors with cores. In this way a medium/high inductance value is obtained in small size components. But using cores has a limitation.
CENELEC has released a new edition of EN 60939-3:2015/AC:2016-04. This standard applies to "Passive filter units for electromagnetic interference suppression - Part 3: Passive filter units for which safety tests are appropriate." The latest edition contains and IEC corrigendum and from April 2016.