Outcharmed!  These have a 1mm Inside Diameter closed ring – which will accommodate a 19 gauge jump ring or smaller.  Because of its low cost, durability and close visual likeness to diamonds, the CZ or Synthetic Cubic Zirconia is a great substitution for diamonds and other gems.  They are 1.7 times denser than a diamond with just a slightly less refractive index.  The CZ is visible from both the front and the back of the setting.  A charming addition to your jewelry supplies!