Twist-on wire connector

Above -Twist-on wire connectors by size and color.
Below - Cross-section of a connector with wires entering.

Twist-on wire connectors are commonly available and cheap way to make connections in circuits. They come in various sizes that are color coded but are only typically used for smaller circuits with wires that are 6 mm² (10 AWG) and smaller. They consist of a plastic body with a threaded spring inside. Two or more wires - solid or stranded - can be inserted into the connector and then it can be twisted, it will tighten around the wires and create a solid connection.

Considerations

• Twist on connectors should always be located inside of a junction box or another type of enclosure to ensure that they are protected against damage or unauthorized access.
• The wires entering a twist-on connector should always be tugged on after installation to make verify that the connection is solid and will not come loose later on.
• The appropriate size connector must be used for the wires that are being connected. Larger wire nuts can accept multiple smaller wires, but they are only designed to accept two of the largest wire that is shown in the chart below.

Color	Wire size
	22 AWG (0.326 mm²)	20 AWG (0.581 mm²)	18 AWG (0.823 mm²)	16 AWG (1.31 mm²)	14 AWG (2.08 mm²)	12 AWG (3.31 mm²)	10 AWG (5.26 mm²)
	0.5 mm²	0.75 mm²	1 mm²	1.5 mm²	2.5 mm²	4 mm²	6 mm²
Gray
Blue
Orange
Yellow
Red