Most quote requests arrive with a product and a quantity and nothing else, which means a round of questions before anyone can price anything. This asks for the specification up front instead.
Start with what you are packing and the rest is pre-filled with sensible defaults you can change. Five short steps — six if you are packing food, which adds the liner — no account, and nothing here commits you to anything. If you would rather read first, the tube size guide covers the same ground in prose.