Threaded Lamp Pipe.....steel threaded pipe will range in color....black, silver or brass. All thread lamp pipe (nipple) is 3/8" OD. This is full thread pipe, you can pass a wire through it. To pass pipe through wood, you need a hole slightly larger than 3/8" diameter. ( In the trade this pipe is referred to as 1/8 IP...but that's a horse of a different color!).