When sourcing reflective wrist bands, the most critical factor is the Retro-reflective Coefficient (R'), which should ideally exceed 330 cd/(lx·m²) to ensure high visibility. You should prioritize materials like PVC, TPU, or high-elastic polyester fabric depending on the use case. For 'slap' style bands, ensure the internal manganese steel plate has rounded edges to prevent fabric piercing, and for Velcro styles, verify the peel strength of the hook-and-loop fastener to ensure it remains secure during vigorous activity.