Twist-On Wire Connectors also known as wire nuts, used to create secure electrical connections.
It consists of a plastic shell, often made of flame-retardant material, and a coiled metal insert. 
The metal insert threads onto the wires, securing them together. 
They come in different sizes, indicated by color-coding, to accommodate various wire gauges and combinations. 
No pre-twisting of wires is required; simply push the stripped wires into the connector and twist. 
They are commonly used in building wiring, lighting fixtures, and electrical appliances. 
Wire connectors provide insulation and protection against short circuits. 
They are widely used in North America but may not be approved in other regions like the European Union for low-voltage wiring. 
They are reusable, making circuit changes and additions easier.

Function: Connect wires without soldering.
Design: Cone-shaped springs inside pull wires in for a firm connection.
Material: Flame-retardant plastic casing, withstands heat up to 105°C (221°F).
Sizes: Different sizes (colors) accommodate various wire gauges (22-10 AWG).
Usage: Strip wires, insert into the connector, and twist until tight.
Rating: Rated for up to 300V.