Feels like 0. 3m PET, could do with strengthening.
"Very thin plastic, that bends out of shape, easily. Thankful to have different sizing options, that can be used with all kinds of releases, but hope another revision comes along, that improves overall strength. This 3 disc case, fits almost perfectly, with my copy of the Mortal Kombat Kollection! :) There is a small gap, but if you shift the product to one side, it will look flush on the shelf (as pictured)."