Premier X5 Sectional Matrix System Universal Matrix Ring Refill uses a proprietary resin material that may be autoclaved up to five times, but is inexpensive enough to be disposable. 35 matrix rings per box. Anatomically shaped matrices allows for proper contouring. Designed to deliver perfect tight contacts every time. Cost effective when switching from expensive NiTi ring systems. Easy to use compared to Tofflemire retainers. PremierÕs ÒXÓ factor is a universal ring made from a proprietary resin material thatÕs autoclavable up to 5 times. The Premier X5 ring has exceptional strength for optimal separation force and stability to deliver perfect, tight interproximal contacts.