Which of these common consumer products was originally developed during WWII specifically for military use before becoming a commercial success?

Throughout history, military necessity has driven remarkable product innovations, many of which later transformed civilian markets. From the development of canned food for Napoleon's armies to GPS technologies initially designed for precision warfare, the military-industrial complex has been a powerful incubator for revolutionary products. This trivia question explores one such fascinating example of military product development that changed modern society.

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Duct tape (developed by Johnson & Johnson in 1942 as 'duck tape' to keep ammunition cases dry)
Post-it Notes (developed as military communication markers for battlefield coordination)
Bubble wrap (created as tactical padding for sensitive equipment transportation)
Velcro (designed for secure closure of military flight suits in high-altitude operations)