Abstract: Modular protector apparatus for oil-filled submergible electric motors that drive submergible pumps comprises pluralities of components that are interconnected in different system permutations to form protectors appropriate for different applications. The components include heads, chambers, bases, and interconnecting bodies. The bodies have fluid passages that are adapted to communicate with other components and that are opened and closed selectively to provide desired inter-component flow paths. By virtue of the invention, a wide variety of protector apparatus may be manufactured economically.