This Magnetic Reference Laboratory calibration tape is used for standardizing azimuth, equalization and determining the "0" operating level or sensitivity of your 2" deck. This tape is for the NAB equalization standard at 355 nWb/m level which is that of the +6 dBm operating level tapes (see section header for a list.) Can also be used to calibrate +9 dBm operating level tapes by setting your repro to show -3 VU rather than 0. Sixteen minutes long.