If you are joining multiple strips of tape lighting, you may need more wire than is included in the kits.
Four-conductor wire is required for connections involving color-controlled lighting, color-controller to lights and light to light.
18 gauge stranded four-conductor wire is supplied as a 26.2' (8m) roll. Rated for indoor and in-wall use, it is a good choice to reduce voltage drop when using longer runs of wire. You can generally run about twice the length of 18-gauge compared to 22-gauge wire. For example, if your 60 LEDs per metre tape is 12' long, the maximum wire length from the light strip to the power supply is 10' using 22-gauge or 20' using 18-gauge.
Note that outdoor installations or those in wet locations, like shower enclosures, require the use of outdoor-grade connectors and wire, in addition to outdoor-grade lighting.