Hey. The factory changed the clear ethyl vinyl acetate (EVA) to a newer and easier to shape EVA, because the customer feedback from the previous version was that it was difficult to shape. For the majority of users, the newer version is easier to shape and holds its shape better than the previous version, which makes the product perhaps a little harder. Of course, the user experiences are also at odds with the new version, so for some the disc works excellently. I myself have noticed that in fitting, the rail needs to be heated sufficiently so that the rail is shaped according to the tooth surfaces and the arch. We pass this feedback on to the factory. bitch.