Closed-end and spring connectors facilitate quick connections through simple twisting or crimping action. Spring connectors feature a live inner spring to maintain a strong connection. Wires are placed into the connector and then rotated to engage the spring. Electrical spring connectors can be reversed to disconnect wires and are available in different colors and configurations. Most spring connectors are designed for use with standard copper conductors. Other closed-end connectors require crimping and are known as crimp caps or crimp connectors. Crimpable closed-end connectors are a cost-effective way to connect a pair of conductors. Similar to pigtail connectors, crimp caps can also accommodate more than two wires. Many of these closed-end connectors contain a tin-plated insert for additional corrosion resistance. Unlike spring connectors, crimp connectors cannot be reversed. As a result, these connectors are ideal for permanent applications.