H21W belongs to Group 1 of the UN regulations. This will help you to gather a lot of information on the usage of the bulbs. If you are like most of the people who know about this group, you are likely already appreciating that you can use the H21W for anything. You are also free to decide where you want to install it on your vehicle.
The majority of drivers use the single H21W solution to replace their car’s reverse light. They understand H21W lamps produce reliable warning lights that indicate to other road users the direction of the vehicle. Moreover, the lamps effectively illuminate the road, which makes it much easier and secure for you to maneuver backward. Also, given the favorable classification, you may use the lamps in reflector and projector headlights as well.
These dual beam lamps use halogen. They produce 21 watts at 12 volts. These light bulbs feature BAY9s sockets. They have a lifespan of about 1,000 hours. If you want to use H21W as headlights, you may need to improve them for better visibility. New generation bulbs, such as LED and Xenon, have a much longer lifespan and produce a better quality of light.