Pressure control equipment; blowout preventer; blowout preventer stack, namely, BOP stack; blowout preventer system; wellbore sealing devices; valves for controlling fluids in well drilling; valves for oil and gas; machinery for drilling and operating wells; fluid pressure control valves; machines for preventing well blow-outs; machines to seal, control, and monitor oil and gas wells; stack test valves for a BOP stack