When sourcing PVC (Polyvinyl Chloride) soles, you must prioritize density and hardness (Shore A). For casual footwear, a hardness of 55-65 Shore A is standard, while safety boots may require higher density. Ensure the supplier provides data on abrasion resistance (measured in mm³ loss) to guarantee longevity and flex resistance, which ensures the sole won't crack after repeated bending. Additionally, verify the slip resistance coefficient, especially if the soles are intended for workwear or rainy climates.