What are the Kindle inserts made of?

The Kindle inserts are printed on Neenah Exact Index 110 lb paper.

It is a sturdy, cardstock-like index paper that gives the insert enough structure to sit nicely inside a clear Kindle case while still being flexible enough to place, remove, and switch out.

The insert is intentionally not super thick or rigid, because it needs to fit comfortably between your Kindle and clear case without causing unnecessary bulk, bending, or charging-port drama.