|Rubber Grommets are generally used whenever wire pass through punched sheet metal or plastic casings for this reason.
Rubber molded and continuous strip grommets, also known as edge grommets, are manufactured in a wide variety of sizes and lengths expressly for this purpose.
Rubber Grommets are usually a single piece which can be inserted by hand. Two piece hard plastic devices are available are available which also grip the wire that passes through. This is called strain relief and is often used on power supply cords that attach to a piece of equipment, to prevent a tug on the wire from stressing the electrical connections inside the equipment.
Sleeved grommets have a flexible extensive (sleeve), usually tapered or molded to flex increasingly towards the free end in order to prevent fracture of electrical insulation.