Traditionally, a "crystal" microdermabrasion system includes a pump, a connecting tube, a hand piece, and a vacuum. While the pump creates a high-pressure stream of inert crystals (aluminum oxide, magnesium oxide, sodium chloride, or sodium bicarbonate) to abrade the skin, the vacuum removes the crystals and exfoliated skin cells. Alternatively, the inert crystals can be replaced by a roughened surface of the tip in the diamond microdermabrasion system.[5]