Which famous product, originally developed for civilian use, became critical to Allied naval operations during WWII by revolutionizing radar detection technology?

Throughout military history, certain products and innovations have dramatically altered the course of warfare. From ancient times to modern conflicts, these famous products often had unexpected origins or applications. This trivia question challenges your knowledge about a revolutionary product that changed military tactics forever. Do you know enough about military history's most influential equipment to identify this game-changing innovation?

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The magnetron cavity resonator (used in microwave ovens)
The transistor (used in early computing)
Nylon fabric (used in parachutes)
Teflon coating (used in artillery shell casings)