When evaluating metal back braces, prioritize medical-grade aluminum or stainless steel stays that provide rigid support without excessive weight. The fabric should be breathable, moisture-wicking neoprene or elastic mesh to ensure user comfort during extended wear. Ensure the Velcro or hook-and-loop fasteners are high-cycle tested (minimum 5,000 uses) to maintain tension over time. For therapeutic products, verify the ergonomic curvature of the metal inserts to ensure they align with the human lumbar spine (L1-L5).