The UTM tools are printed on 30 mil clear stock, and then a protective coating is applied. We use either a film overlay or a UV cured clear coat. Repeated abrasion of the protective coating will eventually wear it off and then the markings will soon wear off as well. For day to day field use they seem to be quite durable. I tested this out by carrying one of the Pocket Corners around in my pocket with my keys and coins for a month. The tool developed a frosted look from the many small scratches it picked up, but the markings were all still there, and the tool was still quite usable.
The 30 mil plastic stock is similar to a credit card in both thickness and flexibility. You can bend the tools in half, without breaking them. When you unbend the tool, you'll have an ugly white crease mark, but the tool will most likely still be usable.