Parentesi lamp, 1971 (1970) Achille Castiglioni and Pio Manz� Rubber, stainless steel, cast-iron, 23 5/8 x 6 x 6" Manufactured and lent by Flos   An adjustable spotlight moves up and down a cable that hangs from a hook in the ceiling and is kept in tension by a cast-iron counterweight which barely touches the floor. The core of this minimal fixture is the parenthesis that gives it its name, the shaped tubular support that holds the light source in place by mechanical friction with the tense cable.