Custom Drawstring Backpack Embroidered, Cinch Bag, Twill Drawstring Ergonomic Travel Draw String Waterproof Backpacking Backpacks 210D Nylon 12" Tumbled Leather Drawstring Backpack Filson RUGGED TWILL BACKPACK The Pros and Cons of Filson Rugged Twill Backpack: A Detailed Review. Sized to fit trimly in the center of the back, our Drawstring Backpack is a timeless design made with heritage materials. The lightly waxed Rugged Twill fabric is sourced from Englands historic British Millerain, pioneers in waxing cotton. The top opening cinches closed with a leather drawcord and cord lock. It's covered by a large rain flap. The Bridle Leather shoulder straps are backed by wide cotton webbing for carrying comfort. Our Bridle Leather has been slowly tanned in natural plant based solutions there is no finer leather.