When selecting metal bases like 925 Sterling Silver, Brass, or Stainless Steel, prioritize hypoallergenic properties and purity certifications. For silver, ensure it meets the 92.5% purity standard to prevent rapid tarnishing. For stainless steel, 316L surgical grade is the industry benchmark for durability and corrosion resistance. Always request a Material Safety Data Sheet (MSDS) to verify the absence of harmful heavy metals like Lead, Cadmium, and Nickel, which are strictly regulated in the US and EU markets.