Halogen wedge base bulbs – W5W, W16W, W21W, W21/5W

The wedge base (or push-in) is a type of mounting where the bulb slides directly into its holder, without a rotation system or bayonet. The electrical contact is made by two metal wires integrated into the plastic base. The most common wedge-base bulbs are the W5W (T10) 5-watt for sidelights, the W16W (T15) 16-watt for the reverse light, the W21W (T20) 21-watt for turn signals, and the W21/5W dual-filament for brake/position lights. This compact format makes quick replacement possible without tools.

The W5W and the W16W both have a wedge base, but differ in size and power. The W5W (also called T10) delivers 5 watts and measures about 10 mm in diameter: it is used for parking lights, license plate lighting, and interior lighting. The W16W (also called T15) delivers 16 watts and has a slightly wider base: it is mainly used for the reverse light. The two bases are not interchangeable due to the difference in dimensions. AGM Vision offers both references in stock.

The W21W is a single-filament 21-watt bulb with a flat wedge base with two identical contacts. The W21/5W is dual-filament (21W + 5W), with a wedge base with offset contacts to prevent reverse installation. Visually, the W21/5W has two visible filaments inside the glass, versus only one for the W21W. The W21W is used for turn signals or the reverse light, while the W21/5W combines brake light (21W) and parking light (5W) in the same bulb. Check the original reference before ordering.

Chrome wedge bulbs (or silver) are designed for clear-glass optics, where you want to hide the color of the bulb when it is off. The chrome coating is transparent to heat and lets orange light (turn signals) or white (reverse light) through once it is on. Versions with ECE approval are legal and pass the technical inspection. Check the "E-mark" mention on the packaging or the technical data sheet. AGM Vision specifies the approval of each chrome bulb on the product sheet in order to guarantee compliance.

Replacing a wedge bulb is one of the simplest operations in car maintenance. Access the bulb holder from the rear of the headlight or light, turn the bulb holder a quarter turn to unlock it, then pull it toward you. The bulb is removed by pulling it straight out of its holder. Insert the new bulb by pushing it firmly in until it stops. The operation takes less than 5 minutes per bulb. No tools are necessary in most cases.

Technically, there are LED bulbs in wedge format (T10, T15, T20) that install directly into the original holder. However, in France, replacing a halogen bulb with an LED is not approved, except for certain recent references bearing the ECE R37 marking. A non-approved replacement can lead to a refusal at the technical inspection. In addition, some vehicles detect the LED’s low power consumption and display an OBD error. Wedge halogen bulbs remain the most reliable and 100 % legal solution.