What does 'loupe clean' mean for a diamond?

A loupe clean diamond contains no inclusions or blemishes visible under 10x magnification, placing it in the FL (Flawless) or IF (Internally Flawless) clarity grades on the IGI scale. These top grades represent less than 1% of all diamonds graded, lab-grown or otherwise. For lab-grown diamonds, achieving loupe clean clarity is more consistently and predictably than in mined stones, because growth conditions can be controlled.