The Easy-Twist WWC-Y-B 500-Count Bag of Yellow Winged Wire Connectors are designed for use on copper wires in the 18-10 AWG size range. They’re made of flame-retardant thermoplastic rated for a maximum temperature of 105˚ Celsius (221˚ Fahrenheit). The quick-grip square spring design grips in fewer twists and can dead-end a single wire, while the ergonomic swept-back wing design and ribbed texture makes them easy to twist. Their compact design is useful for applications in tight areas or anywhere else you need to connect wires