Batteries come in many different shapes and sizes. Determining which one is best for a particular application is straightforward in some cases and ambiguous in others. When hundreds or thousands of cells are combined into packs, the choice of shape is far from obvious. All too often, these decisions are made based on convenience or cost without fully considering the pack-level effects. This paper takes a closer look at the cost of thermal management of cylindrical, prismatic, and rounded prismatic cells in air-cooled packs. The results suggest that when it comes to air-cooling, not all form factors are created equal.