Feng Shui practitioners often recommend using red ribbons, crystals and a number of other objects to balance or redirect the energies called Chi in your environment.  The type of crystals used for Feng Shui are round (spherical), faceted, prismatic, leaded-glass crystal balls (not plain glass balls or mineral crystals from the earth).  The spherical factor is important because the crystal can handle energy coming from any direction.  The facets allow the balls to refract light and emit rays, contributing to the light's expansive nature.  The crystals come in 10 to 70 mm diameters.  Larger crystals are more effective.  Crystals 40 mm or larger are recommended.  Feng Shui cures that are hung, including crystals, chimes, bells and mobiles are always hung using a red ribbon, string  or cord.  The ribbon is cut to a multiple of 9 (whether inches or centimeters) in length.  This does not mean that the chime or crystal ball must hang down from the ceiling in an exact multiple of 9.  You may hang it as far down as is aesthetically appropriate for you.  It is the hanging medium itself that is to be cut to a multiple of 9.  Extra ribbon can be tied at the top if you wish.  Source: Feng Shui Tips For a Better Life by David Daniel Kennedy.