Tungsten Carbide is ranked second hardest next to diamond on the Mohs scale, diamond being a 10 followed by Tungsten Carbide as 9. All of our Tungsten jewelry are Cobalt Free and hypoallergenic. They will not cause skin irritations or turn your fingers green. Due to the Hardness of Tungsten, they can be laser engraved, but not hand engraved. All the products you receive with us come with 30 days money-back guarantee.