1156 Single Socket Bulbs Come in 2 Common Varieties: BA15S and BAU15S
Choosing the right specification is crucial, or you might find yourself unable to install them!
1156 Straight: Officially known as BA15S
Different wattages may have alternative names; for example, a 21W turn signal bulb is also called P21W.
1156 Angled: Officially known as BAU15S
Different wattages may have alternative names; for example, a 21W turn signal bulb is also called PY21W.
How to Differentiate by Appearance:
A. 1156 BA15S:
Two raised points are 180 degrees apart.
B. 1156 BAU15S:
Two raised points are 150 degrees apart.
Refer to the diagram below for a visual comparison:"
If you're not too concerned, you can simply grind down one of the raised points; it won't affect its functionality.