Most high-quality shoe charms are made of Soft PVC (Polyvinyl Chloride) or Silicone. For the international market, it is critical to ensure the materials are Eco-friendly, Non-toxic, and Phthalate-free. You should specifically request EN71 or ASTM certification to ensure the products are safe for children, as these items are often classified as toy accessories. Additionally, verify that the back buttons are securely bonded using high-strength industrial adhesive to prevent detachment, which poses a choking hazard.