This nose screw is made of titanium, which is perfect if you want a nickel-free product. If you're allergic to nickel, titanium is preferable. 

Choose between a gauge size or thickness of 20g (0.8 mm) or 18g (1 mm), depending on what method was used to make your nose piercing. You should also decide whether you want a clear stone in 1/16" (2 mm) or 1/8" (2.5 mm) of diameter. The stone is securely held by four little prongs that prevent it from falling out. No glue was used to fix the clear stone.