Torpedo Hatch Switch Open/Closed J4001 Normally-open, 9/16 – 18 UNF-2A thread J4002 Normally-closed, 9/16 – 18 UNF-2A thread J4311 Normally-open, .625 – 18 UNF-2A thread J4312 Normally-closed, .625 – 18 UNF-2A thread