Racks, handlebar bags, panniers, saddle bags, baskets: They come in all shapes and sizes. About the latter: some come in "small," "medium" and "large." But catalogues usually list their carrying capacities. For racks, it's expressed in weight. But, for bags and baskets, volume is usually more relevant. So, a catalogue listing is more likely to say that randonneur bag or delivery basket is more likely to say that it can hold whatever-number of cubic inches or liters.
I simply cannot conceptualize any number of cubic or square inches, feet, centimeters or meters. When people ask me about the size of my apartment, all I can tell them is how many rooms I have. Or, when I've gone apartment- (or house-) hunting, I could judge a dwelling's size--and then only in a relative way--by looking at it.
On the other hand, it's pretty easy to visualize four, or whatever number of, liters: We all see bottles and cans with that much water, milk, wine or some other liquid. Some catalogue, I forget which, expressed the carrying capacities of its bicycle luggage by the number of bagels or bottles of beer that could be packed into the handlebar, seat and pannier bags--and backpacks--it sold. I liked that even better.
What would they have said about their rain gear? What is the difference between "water resistant" and "waterproof?" Does a bag or jacket have to repel a certain number of raindrops to earn one designation or another?
What if carrying capacities were expressed in raindrops?
