The drop weight test differs, in that the particles are placed on a hard surface and struck by a falling weight. Both tests have been extensively used in the field of comminution. In recent years, however, the drop weight apparatus are being replaced by the twin pendulum. The standard drop weight device is fitted with a 20 kg mass, which can be extended to 50 kg. The effective range of drop heights is from 0.05 to 1.0 m, which represents a wide energy range from 0.01 to 50 kW h/t (based 10–50 mm particles). Following sample preparation the mean mass of each set of particles to be broken is calculated. The results from the drop weight tests provide an energy/input size/product size relationship. This relationship is analysed using a set of curves to describe the size distribution produced from breakage events of increasing size reduction or energy input [3], [4], [5], [10] and [11].