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. Recommended: Especially for those who are planning to upgrade to the Morimoto XB LED headlights with the full LED daytime running light and switchback LED signal. If your Tundra has the OEM DRL relay, it will make the amber turn signal run full-time -- which will cause a premature failure of the turn signal resistors in the lights.