Material: Steel C45, black oxide finish. Handle: Zinc die-cast, plastic coated, black. Screw: Stainless steel 1.4305 (AISI 303).Type GRK: With mounting flat and two radial monting bores, with thread.Tolerance b: +0.08 mm / -0.25 mm. Temperature resistant up to +90°C.Features: does not damage the shaft, stronger clamping force than with set collars, even distribution of clamping forces, precise bores. The disengageable, adjustable clamping lever enables an easy readjustment without tools.