"Special or expensive chips go in the airtites with the foam rim"

Is the "foam rim" like a sponge? I'm wondering because dice are/were sold in plastic boxes that held a set of 5 or 6 dice. Are you familiar with those? The dice were set into rectangles of sponge rubber, which had holes cut to hold the dice. Often, if you find older dice still in the box, the sponge has dried out and left an imprint on the dice. Sometimes the sponge rubber has adhered to the dice. This might not be a problem for chips, as they're made of different materials....but....???

Thanks for any input.
Pam