Sandrin Knives. The hardest (71 HRC) and most durable blades ever made. The blades are made of an innovative variety of tungsten carbide (Polyhedral Tungsten Carbide – PTC) developed and patented by the Italian manufacturer, brand founder, Turmond S.p.A. company. Despite their exceptional hardness, the blades remain flexible and sharp for an impressively longer time than other knife brands on the market (StaySharp ™ technology). The innovative ‘Recoil Lock’ (locking mechanism) completes the overall uniqueness, especially in case of folding knives made by Sandrin Knives.