New Generation Bumper Daylight White - LED SMD DRL | Daytime Running Lights | Car Styling Led Day Light | DRL Lamp

The preferred and most reflective material is an aluminized vapor coating. This is the neat stuff they use in microscopes and in mirrors for aiming lasers. Most of the higher quality lamps use this. Some lights also use a bulb shield, like a cup in front of the bulb. It blocks direct light from the bulb to the lens so that only light from the designed shape of the reflector passes through the lens. This reduces stray light above the cut-off.