Collection: W21W Bulbs

The W21W (T20) bulb: modern vehicle signaling

The W21W is a 21W bulb with a W3×16d plastic base, also known as T20 in Japanese and American catalogs. It equips the rear signaling lights of vehicles produced from around 2005 onwards:

• Reversing lights (white)
• Turn signals (white on vehicles with amber optics, or orange on clear optics)
• Brake lights on some models

Its plastic lug base is more compact and lighter than the metal BA15S base — this is the standard on vehicles with a modern platform.

W21W or P21W: what's the difference?

Same power (21W) but completely different and non-interchangeable bases:

• P21W — metal BA15S (bayonet) base. Bulb for vehicles from 1990-2005.
• W21W — plastic W3×16d lug base (also noted T20). Bulb for vehicles from 2005 onwards.

To identify: look at the base of the original bulb. Metal + bayonet = P21W; plastic + lug = W21W.

W21W LED and CANbus

Switching to W21W LED provides bright white light and a significantly longer lifespan. As with any signaling LED, recent vehicles may detect the low power consumption and display a dashboard error — choosing a CANbus W21W LED avoids this problem.

For turn signals (orange W21W or WY21W), also prefer an anti-hyperflashing version to maintain the normal flashing rate.

See also the dual-intensity version W21/5W (T20) which combines brake light and rear position light in a single bulb.