Choosing a replacement LED bulb by appearance alone creates costly fitment errors. BA15S, BAY15D and BA9S are different bayonet base formats. This technical identification guide helps importers verify a sample before approving a purchase order.
Base identification: what to measure
| Base | Typical shell diameter | Electrical contacts | Identification |
|---|---|---|---|
| BA15S | 15 mm nominal | One bottom contact | Opposed pins at the same height |
| BAY15D | 15 mm nominal | Two bottom contacts | Opposed locating pins at different heights |
| BA9S | 9 mm nominal | One bottom contact | Smaller bayonet shell |
These are nominal base identifiers, not a substitute for an approved dimensional drawing. Confirm the original socket and any market-specific variant before ordering.
Technical identification diagram: inspection sequence
Original inspection schematic (text-based): [1] Measure shell diameter → [2] Count bottom electrical contacts → [3] Compare locating-pin height and orientation → [4] Check socket clearance → [5] Verify voltage and function. A matching diameter alone does not prove compatibility.
Real LEDVEDA product references
LEDVEDA offers a 1156/BA15S S25-15PX2835 version specified at 12 V DC, 2 W, approximately 130 lm and 15 × 2835 LEDs; specifications are model-specific and subject to confirmation against the selected SKU. Compare the 1156/BA15S guide, 1157/BAY15D guide and BA9S guide.
Incoming inspection worksheet for bayonet bulbs
Record the sample’s supplier part number, packaging label, photographed bottom view, side view, shell diameter, overall length, number of bottom contacts and relative locating-pin heights. Use a calibrated caliper and a physical mating socket. Do not force a bayonet bulb into a socket that resists rotation; a near match can still damage the holder.
For a 1156/P21W/BA15S purchase, identify whether the buyer needs a single-function stop, turn, reverse or other approved application. For a 1157/P21/5W/BAY15D purchase, identify both electrical functions and confirm the intended contact assignment. Bulb naming conventions do not override a vehicle manufacturer’s service documentation.
Sample acceptance criteria for importers
- Confirm the base mates with the approved socket without excessive force or play.
- Test the required function at the product’s specified operating voltage and polarity.
- Verify emitted color and brightness against an approved reference, using repeatable conditions.
- Check heat and illumination stability after an agreed warm-up period.
- Compare at least two production samples and retain photographs and an approved reference sample.
For mixed-SKU orders, separate BA15S, BAY15D and BA9S bins and carton labels. Request a packaging proof that shows both the marketing cross-reference and the engineering base designation. See our private-label packaging checklist.
LEDVEDA product photo references
Existing LEDVEDA product photos, not AI-generated base drawings. Verify each individual SKU before ordering.
FAQ
Can a BA15S bulb replace BAY15D?
No direct interchange should be assumed: the bottom contacts and locating-pin geometry differ.
Does 1156 always mean BA15S?
1156 is commonly associated with BA15S/P21W, but verify the socket, voltage and application.
Can a buyer specify only the bulb diameter?
No. Contact configuration, pin position, length, voltage and function also matter.
Request a verified wholesale quotation
Send LEDVEDA your socket photo, base designation, operating voltage, intended function and estimated quantity through our B2B inquiry form. For packaging requirements, review our private-label packaging checklist.