No—the two bulb designations refer to different families and are not generally interchangeable.
7506 and P21W come from separate regional standards and labeling systems used by automotive manufacturers. They describe different base shapes, contact configurations, and electrical ratings, so you should verify the exact base and wattage before attempting a swap. Relying on the numeric label alone can lead to a mismatched bulb and electrical issues.
Understanding the two designations
To explain why a simple swap is often not possible, it helps to know what each code represents and where it is commonly used. In practice, the codes point to different sockets and performance specs that are built around regional automotive lighting standards.
What P21W typically covers
P21W is a widely used European automotive bulb designation. It denotes a 21-watt bulb used in various rear and signaling applications, and it is associated with a specific family of sockets that are common in European-made and -styled vehicles. The exact base and configuration can vary slightly by manufacturer, but the P21W code signals a standard that is not universally interchangeable with U.S.-market bulb codes.
What 7506 typically covers
7506 is a designation used in the United States by several bulb manufacturers for a different dual-function or dual-contact bulb family. The base, electrical contacts, and filament arrangement can differ from P21W, meaning a 7506 bulb will not reliably fit or work in a socket designed for P21W, and vice versa. The 7506 label therefore signals a distinct part from the P21W family.
Key differences at a glance
These are the main categories where 7506 and P21W diverge. The list helps you assess compatibility when buying replacement bulbs.
- Base and socket compatibility: The physical base shape and contact layout are different, so one code does not guarantee a fit in the other's socket.
- Wattage and voltage ratings: The electrical load and voltage requirements differ, and mismatching them can cause fuse or circuit problems.
- Filament configuration: The arrangement and number of filaments can vary, affecting function (such as tail light, brake light, or turn signal).
- Regional standards and common uses: P21W follows European automotive lighting conventions; 7506 is tied to U.S. market conventions; cross-compatibility is vehicle- and manufacturer-specific.
In short, the numbers alone do not guarantee interchangeability. Always check the vehicle’s manual, the installed bulb, and official cross-reference resources before swapping.
How to verify compatibility
Follow practical steps to confirm you select the right bulb for your vehicle. This helps prevent wrong replacements and electrical issues.
- Inspect the current bulb and read any stamped codes on its base or glass to identify the exact base type and wattage.
- Consult the vehicle’s owner manual or a parts catalog for the correct bulb code and replacement guidelines.
- Compare the base type, contact arrangement, and rated wattage between the P21W and 7506 candidates.
- If in doubt, bring the bulb to an auto parts store or contact the vehicle manufacturer for an official cross-reference.
Careful verification ensures you replace with a bulb that matches the required electrical load and socket geometry.
Summary
7506 and P21W are not the same bulb designation; they belong to different standards and are not generally interchangeable. Always verify base type, wattage, and regional specifications before swapping bulbs.
Bottom line: when replacing automotive bulbs, rely on official cross-references and match the exact base and rating rather than assuming compatibility based on a number alone.
What is the Sylvania equivalent to P21W?
7506
Yes part Sylvania part number 7506 would replace P21W.
What does a 7506 bulb fit?
The Osram 7506 bulb is a 12V 21W single element multipurpose light bulb commonly used in automobiles for brake lights. The Osram 7506 bulb can be used to replace any P21W or 1156 light bulb. Osram light bulbs are high quality and are the original equipment light bulbs for most European auto manufacturers.
What are P21W bulbs for?
If you're looking for a replacement car bulb at great value, then look no further than the 382 P21W car bulbs, ideal for use in brake, indicator, reverse, and rear fog lights. Supplied as a twin pack, these bulbs are E-marked and fully road legal so you can drive with confidence.
Is P21W the same as 7506?
The OSRAM 7506 (P21W-382) bulb sold here is the same one that is supplied to the vehicle manufacturers and offers an excellent price to performance ratio with outstanding quality.