The lightbulbs within these fixtures were quite revolutionary at the time this photo was taken. The bulbs featured a standard but larger than usual screw-in base, known as the "mogul" style (that are still made for specialty lightbulbs). Also, the more energy-efficient tungsten filaments within them offered much improved longevity than the carbon-filament bulbs that preceded them; saving users, taxpayers and utilities much money in lighting costs.