When sourcing TPR outsoles, you must prioritize material density and hardness (Shore A scale). For casual footwear, a hardness of 55-65 Shore A is standard, while work boots may require 70+ Shore A. Additionally, verify the abrasion resistance index (typically <200mm³ according to DIN 53516) and flex resistance, ensuring the sole can withstand at least 30,000 to 50,000 flex cycles without cracking. For winter footwear, confirm the cold resistance threshold, as low-quality TPR can become brittle at temperatures below -20°C.