ART Replacement Ball and String for ART Rope Guide. The Rope Guide Ball and String is the original ART ball at 22mm designed specifically for the ART pulleys and rope savers. This is an authentic ART parrel ball only available from the manufacturer. The precise ball size means it slips through the plates on the ART Link and ART Cocoon pulleys but will not pass through the Trapeze (or Winchard) shackle.