Introduced to set the standard as the shape of the Sony MD Walkman. Quite compact, this player is modeled on a "MiniDisc" case. It was the slimmest, smallest, and lightest unit in the industry at the time—a revolutionary size small enough to slip into one's breast pocket or bag without feeling bulky. A new finishing technique gives the unit a distinctive character, in sparkling colors. Three color options were subsequently introduced. Energy-efficient circuitry enables operation at only 1.5 V.