This specification covers two iron-cobalt alloy types currently manufactured and supplied commercially for use in magnetic cores requiring high permeability at and above 15 kG (1.5 T) under d-c and certain a-c conditions. The specific alloy types covered are: Alloy Type Nominal Composition 1 49 % Co, 49 % Fe, 2 % V 2 27 % Co, 0.50 % Cr, balance Fe This specification also covers materials supplied by a pro ducer or converter in the form and physical condition suitable for fabrication into parts that will later be given final heat treatment to achieve the desired magnetic characteristics and where required, mechanical properties. It covers material supplied in form of forging billets, hot-rolled products, cold-finished bars, and strip. The values stated in either customary units (cgs-emu and inch-pound) or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents:therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.