CMI WNR 18-10 Red Wire Nut. Wirenut fasteners, commonly referred to as “wire nuts,” are small, cone-shaped connectors primarily used in electrical applications to securely fasten two or more wires together. Made from insulating materials like plastic, they are designed to twist onto the ends of stripped wires, ensuring a firm and reliable connection. Their design and insulating properties not only ensure a solid conductive bond but also offer protection against electrical shorts. Available in various sizes and colors, each is intended for specific wire gauges and connection types.