Psi is the Greek letter, that is used in many math and physics problems. I created this letter, because I got inspired by the letter (Pi), I created this letter for a necklace , that is why I left a whole, so a string or small chain can fit, the whole is 4.3mm. I think that this model will best fit, with the precious materials.Psi is the Greek letter that is used to represent the wave function in quantum mechanics.Â