The seven-pointed star is called a "heptagram." In Neopaganism, it is often called the Elven or Fairy star; the seven points represents air, fire, water, earth, above, below, and center. In Christianity, the heptagram represents the seven days of creation. The front face of the heptagram is 35mm (1 1/2") high. The cuff itself is about 70mm (2 3/4") across.
Measure the thickness of your wrist, from front to back. My wrist is 47mm (1 7/8") inches thick, and I can just barely get this on. If your wrist is thicker than that, you will not be able to get this on your arm.