CHAIN IS NOT INCLUDEDAvailable in Solid 10K &14K Yellow or White Gold, or Sterling SilverSize Reference:17mm is the size of a US dime21mm is the size of a US nickel24mm is the size of a US quarter We can engrave a message on the back of your Miraculous Medal by altering the size of the symbol on the back leaving room for your engraving. This medal was created after a nun (now Saint) was given a vision of this exact medal front and back. The back features an "M" surmounter by an cross with two hearts and twelve stars. This is the most popular selling medal of all.