Translucent Glass Cabochons, Changing Color Mood Cabochons, Half Round/Dome, BlackSize: about 8mm in diameter, 5mm thick.Please Note: Normal temperature black starts to change color at 14 degreesOur glass mood cabochons have a mesmerizing color-changing effect that makes them stand out. The cabochons change colors as the temperature varies between 15-34 degrees. Please note that the mood glass will not change color if the temperature exceeds 34 degrees, so it's important to keep them at a comfortable temperature to enjoy the full effect.