12mm round. These are premium Japanese cotton pearls made by Miyuki. Though named "Rich Green Black" these pearls are really a beautiful mix of green and purple hue. These pretties are actually made of compressed cotton and then coated with a reflective, shimmery pearl finish. This process produces a very solid and rock hard pearl bead that is light as a feather. These faux cotton pearls are very sturdy under normal wear. Did I mention that these are shimmery? Absolutely stunning. Though called "Rich Green Black" These pearls are actually a mix of green and purple.