For custom components, evaluate the supplier's machining tolerances (typically ±0.005mm for high-end parts) and surface finish capabilities (e.g., polishing, electroplating, or PVD coating). If sourcing cast brass, inquire about porosity control and sand casting vs. investment casting methods, as these affect the structural integrity and aesthetic finish. Always request a First Article Inspection (FAI) report and a pre-production sample to validate the mold and dimensions before proceeding to mass production.