When sourcing COB (Chip on Board) LED down lights, you must prioritize Luminous Efficacy, aiming for at least 100-120 lm/W to ensure energy efficiency. Pay close attention to the Color Rendering Index (CRI); for high-end retail or residential projects, a CRI >90 is essential for true color representation. Additionally, verify the Heat Sink Material, as die-cast aluminum provides significantly better thermal management than plastic-clad aluminum, directly impacting the 50,000-hour lifespan of the COB chip.