OEM timing belt sourcing requires more than matching length and width. This guide explains how engineers and procurement teams should evaluate tooth profiles, pitch and pulley compatibility, rubber and PU constructions, tensile-cord materials, dimensional tolerances, inspection evidence and sample approval. It also provides a practical RFQ checklist and supplier-qualification sequence to help buyers reduce specification mismatch, uncontrolled substitutions and repeat-order risk when selecting an OEM timing belt manufacturer.