When I send something to Canon I use the factory box with factory foam inserts as they were designed to protect the content the best. Last time I received the lens back with one foam cap gone. Today I called to find out where it is and the customer support specialist adviced me not to send the box again as they do not guarantee that they will return the box. In most cases they do but there were cased they did not.
So keep in mind and do not send the box if you want it back. As far as I know absence of the box lowers the resale value.
Once they also lost the warranty card and there was absolutely no way to get it back. Not that I needed it but again I had problem later when trying to sell the lens as the buyer thought it was a grey market or refurbished.


)

