Our packaging type container names are completely arbitrary, although the Tube types do have a special behavior as explained on our shipping help page:
http://www.e-junkie.com/ej/help.shipping.htm
Tubes can also consolidate all Tube-packaged items into any unoccupied capacity in the largest Tubes defined for products in the same order -- e.g., if Product A ships in a Small Tube, and Product B ships in a Large Tube with a Capacity of 2, then an order for 1 unit each of A and B would ship together in just 1 Large Tube, as 1 unit of A can occupy the vacancy in B's Large Tube.
The packaging type you select for a given product does not need to correspond to the actual container you use to pack a shipment -- i.e., you can select an Envelope for the product and still ship it in a box anyway. We only gave container names to our package types as a handy mnemonic to help sellers remember which type is which, rather than naming them more generically as Container A, Container B, etc.
