High speed impact mills with interchangeable grinding elements for size reduction of a broad spectrum of materials with a Mohs hardness of 3 or less. Condux® Universal Mills feature exchangeable grinding elements for versatility in size reduction to d50 ~ 20 µ to 500 µ. Types of grinding elements are attrition grinding discs for size reduction by shear, blast rotor and wing beater for size reduction by impact and shear, pin discs for size reduction by impact, and counter-rotating pin discs for the highest fineness possible with a mechanical impact mill.