Feng Shui : 8 mm beads.
Feng Shui Bracelet: Pi Xiu, a lucky beast in Asia, is a symbol of luck and wealth. Black obsidian bracelet can prevent spiritual attacks and absorb negative energy from the environment.
Obsidian draws in good luck ,  positive energy ,  good health and wealth . 
Its said to be that In feng shui, the color black is connected to the water element. Water represents wisdom, depth, and fluidity. If these are qualities you’d like to bring into your life, it may be helpful for you to work with black stones such as black obsidian.
Water is also connected to career and social network. You might want to bring in more water element through the color black if you’d like to enhance these areas of your life.