Polypropylene

I've been thinking about the strips I need for the bellows. Strips are for example 30mm x 50mm and thickness.. well, what could it be. People suggested to use cardboard; paper board, but for some reason I kinda find it repulsive idea that there was paper board inside the bellows as it's body. Plus, bellows are going to be pretty big, 100cm x 50cm x 50cm, so there's some mass and requirements for the strips also.

So I found a place in Internet where they sell 0.28mm thick polypropylene sheets, sizing 65 x 110cm and price only like 2.0-2.5 euros, so it's kinda cheap when I would need 4 of them.

Looks like there's gonna be a victory with the bellows, too.

(not my pic - Etra)