Abstract: A screening and sizing apparatus for handling clusters or clumps of particulate material in which a roller table is provided with a series of equally spaced anvils or lugs for moving clusters of particulates across the rolls of the roller table and for breaking large lumps or clusters of material by forcing them against adjacent rolls or lugs. An alternative embodiment includes a tramp door through which large particles are passed to a separate bin or receptacle. Another alternative embodiment includes a cooperating, eccentrically mounted cluster breaker above the roller table.