Maintain the effectiveness of a PMD face and body exfoliator with PMD Grey Replacement Discs 6 ct. Each color of aluminum oxide discs indicates the grade of the exfoliation material. Grey discs are suitable for use on very sensitive skin. The grade of exfoliating discs you install in a PMD Personal Microderm Classic, Man, Pro or Personal or Elite Pro model will determine the strength of the treatment. PMD Ultra Sensitive White Replacement Discs and Grey Replacement discs are considered training discs and are the most gentle. PMD Grey Replacement Discs are the second most gentle physical exfoliator.