Good question because typically there is a polarity with LED bulbs. Most automotive 12v bulbs use the metal shell as the ground and have either one or two contacts on the bottom depending on if they have one or two filaments inside the bulb. Both of these bulbs have two contacts on the bottom but are only single filiment. One is for hot and one for ground, the metal jacket is not tied to anything. Doesn't matter which way it goes in on the stock bulb and in the case of the bulbs I bought, didn't matter either.