540 pieces in system case 4.4.1. ISO 4026/4027/4028, steel 45H, plain.
Hardness class 45H corresponds to a hardness of 450 HV
Steel set screws are intended for use under compressive stress only (see also DIN EN ISO 898-5). Typical uses include clamping in an adjusting ring or applying pressure to a counterpart. Steel set screws are therefore extremely hard in order to ensure torsional strength in the hexagon socket during tightening/loosening.