Function:
They create a secure electrical connection between two wires by crimping the metal sleeve onto the stripped ends of the wires. 
Materials:
Typically made with a metal (often copper) conducting sleeve and an outer insulating layer of PVC or nylon. 
Color Coding:
The colored insulation often indicates the wire gauge range the connector is designed for (e.g., red for 22-18 AWG, blue for 16-14 AWG, yellow for 12-10 AWG). 
Usage:
They are used for repairs or new wiring connections in automotive, industrial, and household applications. 
Installation:
A crimping tool is needed to properly secure the connector to the wires. 
Types:
Some butt connectors include heat-shrink tubing for a more secure and environmentally sealed connection. 
Sizes:
It is important to select the correct size connector for the wire gauge being used to ensure a good connection. 
Alternative names:
Butt connectors are also known as splice connectors or crimp connectors.