The moonstones there 3 standard moonstone rings and 3 rainbow moonstone rings, rings are made with sterling silver. 
 
5mm Moonstone ring sizes available - N1/2, O1/2, P1/2
5mm Rainbow moonstone ring sizes available - 2x M1/2 
1x adjustable rainbow moonstone ring around the O- R sizes 
 
One of the M1/2 rainbow moonstone had a natural black fleck in the stone