Premier X5 Sectional Matrices 5.5 mm Refill 80/Package Affordable, reusable proprietary resin rings up to 5 autoclave cycles. Anatomically shaped matrices allows for proper contouring. Designed to deliver perfect tight contacts every time. Cost effective when switching from expensive NiTi ring systems. Premier's X5 factor is a universal ring made from a proprietary resin material that's autoclavable up to 5 times. The Premier X5 ring has exceptional strength for optimal separation force and stability to deliver perfect, tight interproximal contacts.