INSULATION MATERIAL: These electrical wire connectors are made of the plastic shells. The nylon shaped shell has thick walls, high hardness, and is not easy to aging. It can effectively prevent the unstable connection of leakage box and enhance the safety and insulation. STRONG SPRING DESIGN: These Wire Nuts are made of metal spring, which is inserted to ensure a stable connection to each application. Preventing the connection from falling off due to instability. Strong wiring, good conductivity. COMPACT AND PORTABLE: The electrical wire connectors are a round base with model and specification on the top of the wire connector, compact and portable. The packaging is made of transparent plastic molded partition storage box to keep different wire connectors separate. There are 5 kinds of nuts with different colors. Special size corresponds to special colors for easy identification and selection. Clear, easy to store, and use. HIGH-COST PERFORMANCE: Complete specifications, 5 different specifications of wire nuts, special size of special colors.The package includes 50pcs Grey, 50pcs Blue, 50pcs Orange, 18pcs Yellow, 12pcs Red. The most common size can be used for everyday electrical wiring projects and applications.