Stainless steel tubing: 0.032" O.D., 0.006" Wall, 0.019 to 0.021" I.D. $4.50/Foot At just 2.77 HO scale inches, that's scale 2 inch pipe. This tubing slides over the 0.015" music wire used as pushrods in semaphore signals. It prevents the stiction that causes jerky motion. In double head signals this tubing prevents the wires sticking to the control rods. Can be used as traffic signal or sign post. Up to five 36 AWG wires can fit in this tubing. It is made of full hard 316 stainless steel.