These tuning forks are tuned to the frequencies of the human organs. The frequencies were realized by Barbara Hero & The International Lambdoma Research Institute, located in Kennebunk, Maine. She passed sound waves through each organ and calculated their optimal frequency using mathematical formulas based on the speed of sound. Listing of included forks and frequencies: Adrenals & Thyroid 492.80 Hz, Bladder 352.00 Hz, Blood 321.90 Hz, Bone 418.30 Hz, Brain 315.80 Hz, Colon 176.00 Hz, Fat Cells 295.80 Hz, Gall Bladder 164.30 Hz, Intestines 281.00 Hz, Kidneys 319.88 Hz, Liver 317.83 Hz, Lungs 220.00 Hz, Muscles 324.00 Hz, Pancreas 117.30 Hz, Stomach 110.00 Hz. This kit includes 15 tuning forks, and a velvet pouch Our tuning forks are made from a special Aluminum Alloy that is heat treated giving them a very pure tone. The single fundamental frequency will remain constant for up to 15-20 years and the non-tarnishing material will not rust or corrode. Each fork is tuned by hand to an accuracy of /- 0.25% or better. MADE IN USA. Please do not confuse our tuning forks with inferior products being made in China and Pakistan.