Twisted-pair cables are bundles of wires in which each pair of wires is twisted together, as shown in Figure 2-3. Because data normally moves in only one direction through each pair of wires, a 10Base-T or 100Base-T network connection uses two pairs—one for each direction. The most common Ethernet cables include a total of eight wires in four color-coded wire pairs, so you can use the remaining wires as spares.