A universal pump assembly mounts, interchangeably, on a canned motor or on an adapter having an outer magnet assembly rotated by a motor. The pump assembly has a casing with an inlet and an outlet, and an impeller rotatable within the casing to pump fluid from the inlet to the outlet. The pump assembly can have either a mounting ring for attachment to the canned motor, or a containment shell having a cup with an inner magnet assembly and a mounting ring extending from the cup for attachment to the adapter. Mounting features of the mounting ring may be threaded holes or internally threaded posts as non-limiting examples.