As I have discussed earlier, Boston Edison always preferred glass insulators for their low voltage distribution lines. All were side-tie, deep groove, double petticoat designs, notably CD 164, 165, 165.1 and 167. A very great many of these are still in use to this day on their lines. Practically all are commonly encountered variants well-known to collectors. In some instances clear and ice-blue Hemingray spools were used on service racks like the one above.