Plastic. With Pier Giacomo Castiglioni. An inline switch which is the most widely produced of all of Castiglioni's designs, over 15 million have been made since it was first manufactured.

Castiglioni said of the switch: "The object I'm proudest of? A switch for an electric lead I designed thirty years ago with my brother Pier Giacomo. It was produced in large numbers and bought for its formal qualities, but no one in the shops selling electrical materials knows who did the design. It fits snugly in the hand and goes click very nicely... Often when I enter a room someplace in the world and reach out for the lamp switch, I find I'm holding our design."