Filter driers with a solid core are for use in liquid lines in refrigeration and air conditioning plants for fluorinated refrigerants. An effective protection against moisture and acid in the refrigeration plant. Filter driers contain an optimum mixture of silicagel, Molecular Sieves and activated aluminium. Filter driers ensure the greatest possible retention of impurities from the refrigeration plant, and are fitted with a new type of solid core composed of grains of uniform and optimum size. Designed and dimensioned so that they produce only a slight pressure drop, and prevent capacity reduction because of flash-gas in the liquid line.