This rotor fits the Rena Flow 2000 pump UL MOD# M2(S). In addition, it will also fit the Pond Care 450 item 705D. The assembly consists of stainless shaft, bearing/bushing and rotor/impeller. This item should be replaced if the pump's output has slowed even after cleaning or if the assembly is damaged, ie. cracked, blades broken, shaft broken/damaged and missing rubber pieces on the ends of the shaft.