In books production, the Ozalid proof is provided for the entire book and it is for free. It is a low-resolution proof, but it shows imposed pages in correct sequence. It also enables you to review the contents on paper. Please note it is not to be used for color guidance.
Ozalid proof also plays an important rule in packaging production. It indicates die-lines for every component of a packaging at correct sizes. You will be able to check the actual size of your packaging in 2D images.
(Ozalid proof for a book) 
(Ozalid proof for a packaging box)