What is the difference between an IF (Internally Flawless) and FL (Flawless) diamond? FL is the overall evaluation, relating to not only to the clarity, but also other parameters, particularly the cut grade. According to a study, only one in five thousand diamond is rated FL. When I was looking for a 1 ct stone for this unique ring, around the world there were only two jewels available for sale at with this grade, certified by the renowned GIA institute. On the request of my client, I chose better one. It was accompanied by smaller diamonds with a total weight of 0.50 ct, in white gold 750.