Magnaflux Aluminium Test Block (for Sensitivity) Magnaflux| Magnaflux Aluminium Test Block (for Sensitivity) Print Magnaflux| Magnaflux Aluminium Test Block (for Sensitivity) Cracked aluminum test block, which compares sensitivity of different penetrants. MX3501: Aluminium test block for sensitivity. MX14755: Aluminium test block for sensitivity. Request for information