The Toyota Tundra: Has a handful of different specifications for the OEM headlights from the factory and if your truck is setup to power the 7443 halogen bulb in the headlight as a daytime running light  that could cause problems with certain aftermarket upgrades like complete headlights from Morimoto, AlphaRex, or even switchback LED bulbs.

OEM Parts: Are expensive, and are often back-ordered from Toyota  but this solid state DRL Delete relay from Morimoto works just as well, does the exact same thing as the non-DRL spec relay, and is completely plug n play in place of the original.

Switchback Setups: Require this kind of relay on the Tundra because otherwise, your amber mode blinker would stay on full-time.