This nylon fabric was developed to facilitate the need for a smooth, light, and highly durable fabric that could be used to construct parachute backpacks for military paratroopers. The slick fabric surface helped to prevent parachutes from getting caught or stuck within their backpacks and was also strong enough to allow for multiple jumps without becoming worn out or damaged. 420 pack cloth (also called 420 "parapack" fabric, short for parachute-backpack) is a medium-weight, plain weave nylon fabric that features a water resistant DWR (durable water resistant) finish and a clear polyurethane back coating. This fabric is ideal for a wide variety of outdoor and recreational uses.