It's a bag for your tools. Holds other stuff too. It's made of durable PVC coated nylon with welded construction and fold-over velcro-secured flap. This isn't a "dry bag" as the top only folds over once but the contents will stay dry in any situation short of a dunking in the river. The tool bag is a handy place for phone, wallet, compact camera or other essentials and fits neatly in any handlebar bag or front pocket on your handlebar roll.
You get one for free with most of Surly's racks but we have them here separately also. Buy one, put your stuff inside, feel more organized!
7.5" x 6.5"