Art Boards

These are mystery (for the most part) envelopes that have different sized boards.

A4: 8.27 x 11.7 inch
A5: 5.83 x 8.27 inch
B5: 6.93 x 9.84 inch

There are specific anime like Demon Slayer, One Piece and JJK, and some are mixed which include (from what we have seen) Demon Slayer and Ghibli.