An electrical stimulation lead or lead extension includes a body having an outer surface, a proximal end, a proximal portion, at least one distal portion, an outer surface, a perimeter, and a longitudinal length, the body defining an alignment slit extending distally from the proximal end of the body and splitting the proximal portion of the body into two transversely space-apart sections； first contacts disposed along the distal portion of the body； segmented second contacts disposed along the proximal portion of the body, where each segmented second contact extends around less than the entire perimeter of the body and is separated from all other segmented second contacts by portions of the body or the alignment slit； and conductors electrically coupling the first contacts to the second contacts.
