Luxeon CoB Core Range (Gen 4) Lumileds Luxeon CoB Core Range (Gen 4) are high power LEDs with efficacies >,160lm/W for 70CRI and 80CRI products. The LEDs have a small light Emitting Surface (LES) and thermal resistance. Luxeon CoB Core Range (Gen 4) LEDs are hot tested at 85°C thus minimizing additional testing. The CoB Core Range (Gen 4) LEDs are available in 3-step MacAdam ellipse ensuring uniform optical performance in a wide range of applications.