Nyrod is just slang for nylon. It's real name is Golden Rod as Ken is showing. If you have a local hobby shop they have it hanging on a rack. It's the one thing I have found that almost every hobby shop stocks. The stuff has many uses so I try to have a couple packs on hand in my shop. The small inside tube can be used to route antennas and I use it a lot to route my pull/pull cables. The outer tube can also be used for a number of things but it's a bit brittle. It also comes in different colors or even clear.