large early electric unglazed porcelain architectural tube insulator

Large early electric vintage unglazed porcelain tube insulator. Architectural tube insulators were used to allow early bare (or mostly bare) copper wiring to be passed through rafters and wall studs.

This insulator measures 8 3/4" long and 11/16" across the tube. It is 1 1/16" across the tube head. This tube insulator has a center slot rather then a round hole.