Selecting the appropriate material is critical for user safety and effectiveness. For deep tissue therapy, prioritize High-Density EPP (Expanded Polypropylene) or Solid Rubber (TPE/Silicone) as they provide the necessary firmness to reach deep muscle knots. For sensitive users or beginners, EVA foam offers a softer touch. Ensure all materials are BPA-free, non-toxic, and hypoallergenic, especially for products with direct skin contact. On Made-in-China.com, you can find suppliers providing SGS or RoHS certifications to verify material safety.