Plastic would still work in Fastpass machines, as another poster said, UPH are credit card-like passes. Plus when Fastpass first started, people were using anything with a magnetic strip to get Fastpasses, so they do fit. I certainly didn't try it - my mind doesn't work that way. We went to get FPs for Voyage of the Little Mermaid and there was a CM handing them out. It didn't even dawn on us that we could've gotten another FP since we didn't need to use the machine.