Dimension Polyant XPAC VX-21 waterproof fabric exterior. Yellow nylon pack cloth interior. Foam cushioned between fabrics. Emergency whistle zipper pull. #8 water resistant zipper. GripTac lined 2" main strap to secure to frame. 3 position velcro strap for steerer/stem attachment. Interior divider pocket. Yellow nylon packcloth interior. Foam padded side panels.Used by Neil Beltchenko during his CTR record run in 2016 as well as his 3rd place finish in Tour Divide in 2015. Tied for first place in Bikepacker's Magazine Top Tube Bag Throwdown. New items may have black spine. Non-XPAC fabrics in the line-up have the same features but are slightly heavier and less water resistant.