Bulb Size Information
Understanding why car bulbs are designed differently is one thing but it’s also very important to know what they look like.
We’ve carefully curated a table below designed to show you the base of each of our most popular bulb types and a brief description.
The table will hopefully help you understand the different type of bulb bases available.
Bayonet Type Bulbs
| Bulb Designation | Description |
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Designation: 380 Bulb Filament Type: Double Filament Pin Type: Offset / Far Contact Pins: Two AKA: P21/5W |
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Designation: 382 Bulb Filament Type: Single Filament Pin Type: Inline / Far Contact Pins: One AKA: P21W |
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Designation: 581 Bulb Filament Type: Single Filament Pin Type: Inline / Close Contact Pins: Two AKA: PY21W |
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Designation: 566 Bulb Filament Type: Double Filament Pin Type: Offset / Close Contact Pins: Two AKA: P21/4W |
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Designation: H6W Bulb Filament Type: Single Filament Pin Type: Inline / Close Contact Pins: One AKA: 434 |
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Designation: 233 Bulb Filament Type: Single Filament Pin Type: Inline / Far Contact Pins: One AKA: T4W |
Wedge Type Bulbs
| Bulb Designation | Description |
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Designation: 501 Bulb Filament Type: Single Filament Contact Pins: One AKA: W5W |
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Designation: 580 Bulb Filament Type: Double Filament Contact Pins: Two AKA: 7443 or W21/5W |
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Designation: 582 Bulb Filament Type: Single Filament Contact Pins: One AKA: 7440 W21W |
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Designation: 955 Bulb Filament Type: Single Filament Contact Pins: One (LED’s have 2 for polarity) AKA: W16W |
Headlight Bulbs
| Bulb Designation | Description |
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Designation: H1 Bulb Filament Type: Single Filament Contact Pins: One Base Width: 21mm |
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Designation: H4 Bulb Filament Type: Double Filament Contact Pins: Three Base Width: 43mm |
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Designation: H7 Bulb Filament Type: Single Filament Contact Pins: Two Base Width: 30mm |
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Designation: H15 Bulb Filament Type: Double Filament Contact Pins: Three Base Width: 35mm |
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Designation: HB3 Bulb Filament Type: Single Filament Contact Pins: Two Base Width: 30mm |
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Designation: HB4 Bulb Filament Type: Single Filament Contact Pins: Two Base Width: 30mm |
Author: Dean Michael
THIS IS BRILLIANT ! (in every sense)
Thank you so much for this EXCELLENT guide on lamp base fittings…it is a much needed clear and detailed description of an otherwise confusing set of codes. To whoever compiled this crystal clear guide – I congratulate you – (someone who actually seems to know what they are talking about, and which therefore gives me some confidence in your companies products !)
Very Helpful !