Diode Dynamics DD2278 Red Halo Ring BulbHDHalo Technology. These HD LED halo rings have been designed from the ground up to be absolutely the brightest, most reliable halos physically possible. Each halo is populated with a large number of high density (HD) LEDs, which are then coated by a diffusing gel, resulting in a perfectly uniform light when turned on. When off, the diffusing gel hides the chips, resulting in a clean, OEM appearance. Sizing: All sizes are listed by outside diameter,