If you are joining multiple strips of tape lighting, you may need more wire than is included in the kits.
14 gauge stranded two conductor outdoor-rated wire is supplied as a 26.2' (8m) roll. A good choice to minimize voltage drop over long runs, outdoor or indoor. Its two-conductor format is directly suited for use with white LED lighting (tape or spot). Although its stranded format is incompatible with the wire-ready connectors used for outdoor tape lighting, it can still be used to minimize voltage drop over long outdoor runs; just connect a short length of 18 gauge solid-core wire between it and the tape lighting. This wire is also well-suited to bridge long distances between the power supply and color controller of color-controlled tape lighting installations.
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.