Description The EnvisionTEC E-Shell 500 series has been designed especially for applications in the Hearing Aid industries and is distinguished for soft durability. The material is used on Perfactory UV machines only. EnvisionTEC E-Shell 500 is a liquid, photo-reactive acrylate for building functional parts. It is CE certified and Class-IIa biocompatible according to ISO 10993 (Medical Product Law) for soft ear shells and tips. They are tough, water- and perspiration-resistant and available in several in two variations clear and opaque pink.