Magnaflux Tool Steel Test Ring - CertifiedMagnaflux Tool Steel Test Ring The Tool Steel Ring is a standardized test piece commonly used with wet bench magnetic particle equipment. The ring is machined from AISI O1 Tool Steel, annealed, tested and certified to meet AS 5282 specifications. Typically used with a 1 inch central conductor, the Tool Steel Ring has 12 machined holes at increasing depths from the edge and is used to verify the performance of HWDC, FWDC, and 3 phase FWDC magnetizing