FL, or flawless, is the highest clarity rating for a diamond. Even when examined at 10x magnification, the GIA only grades a diamond as perfect if it has no flaws or blemishes visible to a skilled grader.
Things get a little more challenging and subjective when it comes to determining the appropriate clarity grade for each diamond shape and budget.
There is no single “optimal” clarity grade for every type of diamond because diamonds come in a variety of shapes and cut quality grades.
This is because different cutting styles of diamonds exhibit inclusions in different ways. Asscher cut diamonds, for example, which are a stepped cut faceting style, may be more likely to have more visible inclusions than round brilliant cut diamonds, which are cut for maximum light reflection.