H1H3H4H7H11HB3HB4HIR2H8H15 (715)H9 (709)H13H16HB3 / HB4H6W (433c/434)H8/H11/H16C5WW5W (501)P21W (382)P21/5W (380)PR21/5W (380R)PY21W (581)T4W (233)WY5W (501A)W21WW21/5WP13WW16WPS19WPSX24WH27

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H7 (499)9003 (HB2/H4)H11H1 (448)HB3/HB49005 (HB3)9006 (HB4)H8/H11/H16HIR2H16W5WPY21W (581)P21/5W (380)P21W (382)C5WW16WW21/5W (580)W21WWY21W (582)WY5W (501a)T4W (233)




If you've spent some time shopping for the best bulbs for your car, you will have actually come throughout all the different bulb classifications. Tbelow are many forms of bulbs - H1, H3, H4, H7, H11, HB3, HB4, and many more. But, several motorists don't know the distinction in between these bulbs. In this write-up, we'll take a look at these widespread bulb forms and also exactly how they differ from one an additional.

Bulb classifications

Tright here are numerous various classifications for auto bulbs. The United Nations (UN) has actually collection worldwide standards for classifying auto bulbs. This helps to ensure that bulb types are typical throughout different nations.

UN Regulation 37 additionally provides guidelines on how each bulb kind can be used. Bulbs are grouped right into 3 categories. Group 1 can be provided for anything, consisting of headlights, tail lights, and more. Group 2 have the right to be offered for signalling lights, yet not for bulbs that illuminate the road. Finally, Group 3 are lights that are no longer supplied on new vehicles however have the right to be made as replacements for older vehicles.

All of the bulbs discussed in this short article - H1, H3, H4, H7, H11, HB3, and HB4 - are in Group 1. These bulbs are generally supplied as headlights as a result of this classification. Even though these bulbs are in the exact same category, they"re not interchangeable. Whilst an H1 and a H7 bulb might look the exact same in terms of light output, an H7 bulb won"t fit right into a socket for an H1 bulb.

This indicates that you must stick to the bulb fitting that your vehicle supplies. If you"re not certain which fitting you require, you can check your owner"s hand-operated or use the bulb finder on this page. 

Comparing bulb types

Regardless of their similarities, each of these bulb types is slightly different. They differ in variety of filaments, nominal power, and also base kind.


Some bulbs have actually only one filament, however others have 2. Also well-known as dual filament bulbs, these are used to power both the primary and also dipped beam of your headlights. One filament is dedicated to each function. This can be less complicated for motorists, as you just have actually one headlight bulb. Cars that use single filament require one bulb for the primary and also one more for the dipped.

H1, H3, H7, H11, HB3, and HB4 bulbs are single filament. H4 are dual filament.

Nominal power

For the many component, these fittings all produce the exact same amount of light, yet the variety of volts they require and watts they create (likewise dubbed nominal power) is various for each bulb. To make points even more complex, many of these bulbs are easily accessible with different nominal power ratings.

Because each bulb requires and also outputs a slightly various amount of power, it"s dangerous to switch one bulb fitting out for another, for example, switching an H1 for an H7. Think of it prefer plugging an Amerideserve to appliance right into a European power outlet - this deserve to reason the appliance to overheat or end up being damaged. The same could happen through automobile bulbs. Luckily, each bulb fitting has actually a distinct base that renders them hard to confusage through each other.

It"s worth noting below that troubles will largely happen when switching in between fittings. If you desire to upgrade your bulbs, you shouldn"t have actually any kind of problems with any wattage or voltage readjust, unless you"re installing an afterindustry kit. Upgrade bulbs from a trustworthy source such as chrischona2015.org are perfectly safe to install and use.


The base, or cap, is the bottom component of the bulb that connects to the socket. These different bases are one more part of what provides it impossible to simply switch in between fittings. For the a lot of component, consumers do not need to problem around the base of their bulb other than to ensure it fits your vehicle.

Once you"ve established which bulb fitting your automobile uses, you can shop our selection of H1, H3, H4, H7, H11, HB3, and HB4 fittings for the best headlight bulbs. Struggling to decide what type of bulb you want? Check out this blog post that breaks down the differences between styling, performance and longlife varieties.

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About the Author

John Conboy is the founder of chrischona2015.org, a UK based automotive lighting specialist, which ships bulbs international. John has actually 20+ years endure in the industry and in that time has become an approved partner of Philips and also OSRAM.