FOUR STAR is the top-selling knife series of ZWILLING J.A. Henckels worldwide. Honed and hand-finished by the most skilled artisans, this celebrated collection is the model of safety, ergonomics, and comfort. Thanks to their seamless transition from bolster to handle, the knives are comfortable to use for long periods of time. The bolster provides the right balance while acting as a safe finger guard.The knives are made of proprietary special formula steel that has been perfected over the years. Combined with ZWILLING's signature ice-hardening technique, these FRIODUR blades are harder, sharper, they will NOT STAIN or chip and they retain their sharpness longer. Precision-forged from a single piece of steel, the SIGMAFORGE knives have an exceptionally sturdy, balanced and flexible blade. Manufactured in Germany Special formula high carbon NO STAIN steel SIGMAFORGE knife is forged from a single piece of solid steel Ice-hardened FRIODUR blade starts sharper, stays sharper longer, and has superior resilience Precision-honed blade and laser-controlled edge ensures ideal cutting angle for sharpness and durability Ergonomic polypropylene handles permanently bonded for seamless accuracy and gaps 57 Rockwell Hardness = excellent edge retention Edge angle 15 degrees per side