This is a mood ring, meaning the stone changes color based on temperature. The mood "stone" is oval and 18x13mm in size (12mm=1/2 inch), and is made of acrylic.
The filigree band is made of zinc alloy (a nickel free metal) and is an antiqued silver color. The ring is adjustable and should fit sizes 6-8 comfortably. It can be sized smaller (band overlaps) or larger (band gap is larger), but some may feel it not comfortable.
A paper with the color "meanings" is included.
Blue: relaxed, calm
Green: active but not stressed
Gray or Amber: anxious, stressed
Violet: Happy, passionate and romantic
Mood ring womens adjustable ring color changing ring with filigree band listed in: