T20 vs 3157: Complete Guide For The Most Commonly Confused Twin Bulbs

Many car owners confuse T20 and 3157 bulbs because they look very similar online.
However, these two bulb bases are different and are not directly interchangeable.

Choosing the wrong bulb may cause poor fitment, socket damage, or even a blown fuse.

1. Check the Plastic Base

The easiest way to tell them apart is by checking the side of the plastic base.

• 3157 / 3156
  Usually has a raised anti-misplug tab on the side.
  Commonly used on American vehicles.
• T20 / 7443 / 7440
  The base is usually smoother without the raised side tab.
  Commonly used on Japanese vehicles.

2. Check Single-Function or Dual-Function

You can also check the contact wires at the bottom.

• Dual-function bulbs:
  7443 / 3157
• Single-function bulbs:
  7440 / 3156

A dual-function bulb can usually fit into a single-function socket because the extra wires only touch the insulated plastic area.

3. Be Careful with SRCK Sockets

Halogen bulbs are usually non-polarity, but LED bulbs can be polarity-sensitive.

If a regular dual-function LED bulb is installed into an SRCK socket, it may cause a short circuit and blow the fuse.

For safer installation, we recommend using a non-polarity LED bulb, which can work with both standard and SRCK sockets.

Need Help Choosing the Right Bulb?

Before ordering, please check your original bulb, socket type, and vehicle model.

Not sure which bulb you need?
Send us a photo of your original bulb and socket, and we’ll help you confirm the correct replacement.

Know More: https://www.paledbulb.com/