Up for sale is a speed/flutter, azimuth calibration cassette for cassette recorders and players. For the speed adjustment a signal of 3khz at 0db has been recorded on the side A of cassette. You will need a multimeter with frequency counter option hooked up to line out of your deck or your phone with a frequency counter app. Just adjust the speed adjustment pot to set the frequency as close to 3000 Hz as possible. For the azimuth adjustment a signal of 10khz at -10db has been recorder on the side B of cassette. You will need a multimeter hooked up to line out and adjust the azimuth screw measuring the maximum ac voltage you can get. I used my late serial number Nakamichi Dragon to record the 3 Khz test tone as the tape speed is factory adjusted and fixed and the W&F of the deck is close to 0.015%, maybe the lowest you can get from a cassette deck. To record the 10khz test tone I calibrated the playback head of my BX-300 deck using a new sealed BASF IEC/DIN standard calibration tape (picture n.4) and my oscilloscope, and each test tape I record, I use the oscilloscope to calibrate the record head as much accurate as possible, just to prevent any cassette shell imperfections. I use only NEW TDK D-30 or Maxell C-30 cassettes. This cassette is not an original test tape, but you can get pretty accurate results adjusting your deck using it. Check my feedback for this item. I moved recently in US from Greece, where I was working in Greek Nakamichi service during 90s and I have all the professional equipment (original test tapes, oscilloscope, wow & flutter meter, distortion meter, frequency response meter). If you need to service your deck Ill be happy to help you. See also my other items and my feedback. Thank you for looking.