To better understand the different types of BA15 bases. These are all bulbs with a 15 mm diameter metal base.
This type of bulb is used for parking lights, turn signals, fog lights, brake lights, and tail/brake lights.
BA15 bulb types with offset pins are BAU15S, BAZ15D, BAW15S, and BAY15D:
BAU15S (pins offset in one direction, 30° view from below)
This is a PY21W 12V orange bulb. It is a bulb for the turn signal light.
BAY15D (pins offset in one direction, side view)
This is a bulb for the tail/brake light. A double-filament bulb: the P21/5W. It is available in several models: long-life, red and orange color, or in power: 21/5W, 24/8W, or 28/7W. It is also available in 6V, 24V, and 48V. The entire range of BAY15D 12V bulbs is available in our BAY15D collection.
BAZ15D (pins offset in 2 directions, 30° view from below and from the side)
Also known as P21/4W. This is a double-filament bulb for the tail/brake light. A 21W filament for the brake light and a 4W filament for the tail light.
BAW15S (pins offset in 2 directions, 30° view from below and from the side)
This is an original Philips brand bulb, also known as PR21W. A single-filament bulb with pins offset in 2 directions.
It is always red. Often used for fog lights, but also for brake lights.
BAW15D (pins offset in both directions)
This is a red bulb for the tail/brake light. It is a double-filament bulb, the PR21/5W. It is widely used for Thule bike racks.
BA15 bulbs with symmetrical pins
The BA15s bulb mainly exists in 2 forms: "large" pear-shaped or "small" globe-shaped.
BA15S — P21W
This is the most common bulb along with the BAY15D.
The pear-shaped BA15S bulb is the P21W. A bulb for the turn signal, but also for the brake light or fog light. In most cases, these 3 types of lights have a power of 21W.
BA15S — R5W / R10W
Also called a grease bulb, the BA15S R5W or R10W with a globe-shaped glass is smaller in size (height). It is often used for parking lights. This is the first position when you turn on your lights. These lights are normally 5W.
A BA15s bulb always has a single filament with symmetrical pins.
This applies to the P21W, R5W, R10W, etc.
