This metal box boasts twin mixing pallets and a lift out tray which holds the pans and can be removed to allow cleaning of the inside of the box.
The approximate size of the box is 22.5 cm wide x 12 cm long x 2.5 cm deep.
This metal box is sold empty. The image below shows how snuggly it holds the White Night Watercolour full pans.
See here for a smaller 12 pan metal box.