Why don"t bi xenon lights fit in a 1990 F150? I know there is the circular thing that lock in the light but why cant a bi xenon bulb fit in with this? If anyone knows the answer please let me know. Thanks.

 

As mentioned, I've tried to install our Bi-Xenon bulb into my friend's 1996 F250 it fits but because of the black circular locking tube it prevents our Bi-Xenon bulb to lock onto the headlight.
Because of the circular tube it won't allow our Bi-Xenon bulb socket to align with the socket on the headlight. This only happens with the older Ford trucks/SUV. Where the new models don't have the circular tube.
But our regular Hi/Lo will fit regardless the year of the trucks.