Large foldable sheet music holder with a steel extension arm, to
  be screwed onto vertical stand tubes. The clamping range for the
  tubes lies between ø 11 and ø 30 mm. The distance of the sheet
  music holder to the stand tube can be steplessly adjusted on the
  extension arm ranging between 185 and 265 mm. The sheet music
  holder is clamped and aligned by means of a handy wing nut. For
  transport, it can be folded and retracted to save space.