A blowout preventer assembly is provided and is generally configured having an upper housing, a lower housing with a plurality of internally interconnected cylinders, a one piece energizing ring, and a plurality of individual bottom cover plates all enclosing a lower housing column bore for receiving well pipe. The blowout preventer assembly also has a plurality of annular pistons, a plurality of associated glands disposed in each cylinder with each piston, a main seal with a plurality of main seal ribs, an adaptor ring, and various dedicated and associated seals and threaded attachments.