Quote Originally Posted by radargeek View Post
Resurrecting a somewhat old thread, but I wanted to ask... when heads are supposed to be a maximum of 22-24" apart, is that inner edge to inner edge, center to center, or bubble to bubble?

Also, to give my 0.02 regarding bubbles in or out, although with the small ALP heads it doesn't matter that much, I prefer bubbles out due to the curvature of the grill, having them out allows the receivers to have a better "view" with the heads flush or slightly recessed. Thus you can have a bit more stealth without any loss of performance.
There is no hard set rule.. Its usually best to post a photo and have us give recommendations based on the vehicle.