The inner diameter is exactly 16, as measured with an inner diameter gauge. The color is a bit difficult to describe, but it's a pale gray-like color with hints of pale green and purple. The beads are small, 6mm, so it might be hard to see, but when you roll them around, they sparkle with pyrite (o^^o) Meaning and Effects as a Power Stone It is known as a power stone that combines the meanings of pyrite and fluorite. Fusion of intelligence and action: Fluorite (also known as the "stone of genius"), which clarifies thinking, and pyrite, which brings out positivity, are combined, and it is believed to have both clarity of thought and the ability to take action towards self-realization. Evil warding and protection: Pyrite has long been called a "guardian deity" and is said to have powerful effects against evil and disaster. Good luck and prosperity: It is also said to bring good luck and prosperity to the wearer. Enhancement of concentration and creativity: It is also popular as a charm for those who want to improve their concentration and creativity in their studies and work.