The Magnaflux® Magnetic Particle Test Bar is used as a test piece with artificial flaws to establish field direction and determine adequate current levels using AC or DC current in wet horizontal magnetic particle bench units. The bar contains both fine and coarse defects, surface and subsurface defects, and longitudinal and transverse indications.

As required in some specs, this bar may be used to determine that the MPI procedure has the ability to detect a 1/16 inch long by .006 inch wide by .01 inch deep notch (maximum dimension) oriented 90 degrees to the magnetic flux. It is made of low alloy steel and is filled flush with a non-conducting material to prevent mechanical holding of the magnetic particles.