Which metallic binder is used can have an effect on the final product. For instance, if a tungsten carbide ring is made with cobalt, then it may cause a rash on the finger of the person wearing it, or it may tarnish by coming into contact with the oils produced by a person's skin. Nickel on the other hand does neither of these things, and it creates a safer, more durable product. Unfortunately though, nickel is much more expensive. So like any product, the particular components required should be taken into account before manufacturing to be sure that the final result has all the necessary attributes.