Like any other filter, this one protects the front lens from water splashes. 

I have not looked for a specific travel case, but unless you are being really rough with it I would say a padded envelope or a generic small case would do it. It's pretty sturdy. I take it to to the office sometimes and just put it in one of the pockets of my laptop case. Also, for extra protection against scratches I never removed the clear plastic film that comes over the screen. Except for the red ""pull here"" tab, you can't tell it's there. 

The packaging is all matched with a hard board to ensure that the user receives the product in perfect condition 

Hi, if you wand add other filter on the front of this nd filter , it would be larger one size than this filter , the 82mm nd filter need 86mm lens cap or other filter, thanks 

1. No, 82mm filters can only be bagged on 82mm lenses.