The materials needed for a re-usable box are: 10"x10"x4" cake box, coated gift bags to seal the inside and outside of box, trash bags to be used as disposable liner (24" wide and 30" tall), 2 acrylic place mats (30 cm by 45 cm minimum size, longer would be better), and 4 extra-large, heavy duty paper clips.

We've been using this box for over 2 years. You might notice the silver duck tape in the englarged picture (just click on the photo) -- RC loves to scratch so that's one of the reasons we added the acrylic place mats to the configuration.

RC's re-usable litter box set up and -- almost -- ready for use. I set this up just for the photo, so I skipped adding litter and the plastic bags.

Hopefully, the picture is able to give you an idea how a portable litter box works.

Packed and ready to go.

We place the plastic bags and folded box between the acrylic place mats and use the heavy duty clips to create a compact package that can be easily extracted from the side pouch of our roll-on suitcase.

We have 2 heavy duty re-usable plastic bags -- with a zipper. Each bag holds about 3 kilos of litter. If our journey is a long one, then we put one of the bags in the luggage we check with the airline and store the other in our roll-on baggage.