Abstract: Apparatus for grading objects according to size comprises a grading array of spaced apart grading rollers which allow objects smaller than the roller spacing to pass between adjacent rollers but retain objects larger than the roller spacing. Support members are provided capable of assuming different degrees of curvature, for example endless conveyors, and the grading members are mounted on and spaced from the support members by mounting elements which extend outwardly from the support members. A mechanism for varying the curvature of the support members, such as a leaf spring on which the support members rests, causes the grading rollers to spread apart or to come towards each other so as to vary the size threshold of the grading array.