This waterproof rain cover is designed specifically for Essential Packs EP-FLEX Backpacks (Version 2, 3, 4, 4Z and PRO). To use, simply stretch the rain cover around the backpack. To store, roll up the rain cover, then keep it bundled using the built-in Velcro strap. This rain cover is 100% waterproof and protects your backpack and it's supplies in rain, storms, and hurricanes. It also features highly visible "EMERGENCY" printing on the front. An essential accessory to protect your emergency supplies in wet and stormy climates.