A disc for releasable attachment to a shaft of a disc screen apparatus includes a hub having a bore and a single split defining a pair of opposing ends. The hub also has at least one flexible portion intermediate the opposing ends that permits the opposing ends of the hub to be separated a predetermined distance sufficient to allow the shaft of the disc screen apparatus to pass between the opposing ends into the bore. The hub has plurality of outer impacting portions configured for engaging materials to be classified and propelling the materials in a conveying direction when the hub is rotated. A mechanism is provided to secure the hub to the shaft so that the shaft extends through the bore.