The coupling above the street light fixture connecting it to the end of its gooseneck bracket typically was a glass CD 280 or a similarly styled pintype insulator in porcelain. The top of the fixture had a standard one-inch cast iron pin as part of it. A clamp went around the insulator's wire groove affixing the fixture to the pipe bracket's end. In addition to its physical purpose such insulators electrically insulated the pole bracket from the fixture's potentially dangerous wiring. Street light fixtures of this design were used through the teens. Subsequent ones through the decades had a large porcelain housing (typically green) that held the socket, reflector and wiring to its metal bracket.