Small-diameter electronic shrink tubing works well for flexible cables and is readily available in several sizes and types. I obtained 1⁄16" clear and ⁹⁄64" black tubing, just what I needed for fuel lines and control cables on a motorcycle model I recently built. Just hold one end and rotate the tube over a heat source (a soldering iron works well) until it has shrunk completely.
Tip submitted by:
Tom ZuchowskiClemmons, North Carolina