Manufactured by Mitsubishi materials, all three types of precious metal clay (PMC)- PMC Standard, PMC +, and PMC 3 consist of precious metal (silver) in powdered form, a non-toxic organic binder (clay) and water. The differences between the 3 types are firing times, firing temperatures, and shrinkage rates. These variances are the result of differences in the particle size of the metal, and the percentages of the binder within the clay. PMC+ is the most popular of the 3 PMC options. It is still quite moldable, but more dense than original PMC, resulting in a stronger more durable finished piece. PMC+ has a low shrinkage rate of about 10%, its low shrinkage rate makes it wonderful for creating items such as rings that must be accurately sized. The lower firing temperatures allows you to set man made stones, ceramics, and enamels within the clay. PMC+ can be fired at 1650 degrees Fahrenheit for only 10 minutes, 1560 for 20 minutes, and 1470 for 30 minutes.