For those wondering about the durability of this long-term, I've worked in plastics manufacturing and can give some insight: Based on the visual properties, it looks like it's an 90/10 blend of recycled crumb rubber mixed with a polypropylene binding agent, possibly something like KW621. We've used similar blends to manufacture impact-resistant items. The good news is that it'll hold up decently to stress and impacts, along with general wear. The bad news is that designs which introduce too many punctures to the material will cause it to fall apart relatively fast, since it's more rubber than plastic. Rivets are probably better than stitching long-term. Also, it'll burn just like a tire and catch pretty easily (depending on how low the polymer content is). Don't use it for anything that might come into contact with food or yourself regularly, though, crumb rubber is nasty stuff which leaches an absurd amount of carcinogens.