This is the best way to inspect the correct iunstallation of those bulbs. Take the bulb out and you will see that it has a **** on it. Now use an inspection mirror and look inside the housing where the bulb goes. You will see that it is slotted and has a recess that the **** fits into. Orient the bulb accordingly and slide it into the housing. When it is correctly installed; you will not be able to rotate it in the housing. Hope this helps!

James