Clarity ranges from the best grade of FL, down through IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2 until I3. Clarity refers to the number and density of inclusion in the diamond. Most diamonds contain some inner flaws, or inclusions, that occur during the formation process. The visibility, number of inclusion, location and size of these inclusions determine the clarity of a diamond.
When the inclusions are discernable in the diamond under a 10x magnification lens it can be said as an ideal clarity (a clean stone). Inclusions greatly affect the beauty and value of a diamond because they absorb the light rather than allowing it to be reflected back through the front side of the stone.
Depending on the presence of internal and external imperfections present in the diamond, it is graded for its clarity. Clarity ranges from the best grade of FL, down through IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2 until I3.