I don't know what that shiny material is called, but over the last several months, I've come to find that it has a fairly high fraying factor – and apt to rip in the seams. But I've learned a few things since I first put these capes together and with a little intensive care this past weekend, I hope I've managed to fix them for the long run. I also replaced the original snap button with some Velcro, which will with any luck mitigate a lot of "Mommy, will you help me take off/put on my cape?"