Interestingly, the shapes are not standard. The lengths and diameters vary a little from cell to cell, and quite significantly from cell type to cell type (Yes,

Interestingly, the shapes are not standard. The lengths and diameters vary a little from cell to cell, and quite significantly from cell type to cell type (Yes, I'm talking 21700 from one manufacturer vs 21700 from another manufacturer, and different models of 21700 from the same manufacturer). That's just the tip of the iceberg, never mind the actual cell performance. In pack manufacturing, you cannot swap cell types out easily. I could go on... That's why they are making the cells near the pack assembly facilities. It's because they are planning to use those specific cells.