Phi Ratio Tuning Fork Set! The 288hz & 468 hz Tuning Forks are middle D and A# frequencies in the Pythagorean Scale.

Pythagorean tuning is a system of musical tuning in which the frequency ratios of all intervals are based on the ratio 3:2. This ratio, also known as the "pure" perfect fifth, is chosen because it is one of the easiest to tune by ear and because of importance attributed to the integer 3.

Nikola Tesla once said "If you only knew the magnificence of the 3, 6 and 9 then you would have a key to the Universe."

Interestingly, the Phi Ratio is found in 2 of the Platonic Solids, which are the geometrical building blocks of all physical + metaphysical realities.
 
The 2 it occurs in are the Icosahedron and the Dodecahedron...the Dodecahedron represents the 5th element Aether or Spirit, which was once so heavily respected + revered in Greek Mystery schools, you could be killed for mentioning it outside their doors.

Phi, or the Golden Mean, shows up EVERYWHERE in nature. From the anatomy of a butterfly to the distance petals or leaves grow, in the nautalis shell, the proportions of the human body and more. And it's been utilized in the most praised art and sacred architechture all over the world.

Whatever theory you want to subscribe to about the Phi ratio, it seems to be an invitation into the Mysteries. 
 
They don't call it the Divine Proportion for nothing!

Each Phi Ratio Tuning fork set comes with both forks, a striking mallet, and velvet bag.