The Miss Poppins' Top Tube Bag is supercalifragilistic and expialidocious. It is the first of its kind. The bag is able to hold as little as needed, but not limited to the usual amount of space. This bag can expand and contract as needed. There is an external slot for a phone or map that will get tucked under the roll of the bag. The cord on top is adjustable and you can move it around to get the best fit. The Miss Poppins' attaches to the bike via two 9" Voile straps and a cord that gets looped around the stem and steerer tube spacers.
There is HDPE plastic built into the walls to give the bag more structure and keep it stable when riding aggressive trails or roads.