get out a clean and dry dish sponge, and then wrap it in sandpaper. The foam material of the sponge contours the paper around the edges of wood or drywall when you apply gentle pressure.

Ask Corporation explains how to remove the foam as follows ... It is worth noting that it's not the only sponge material attached to Sapphire cards, though not all need removing.

Cymat’s Aluminum Foam, marketed under the trade name of Alusion™ for architecture, is an extraordinary and versatile material with ... appearance to a metallic sponge, Alusion™ is visually ...

Cellular cast aluminum foam, sound absorbing properties, strong yet lightweight panels, versatile material ... are similar in appearance to a metallic sponge. It is visually striking, with ...