Grommet

This type of protective bushing is quite common in applications that range from telecom switches and data center cabinets to complex and dense wire/cable and even hydraulic tubing in aircraft, transportation vehicles and medical equipment.

[2] They can be made of metal, rubber, or plastic, and are easily used in common projects, requiring only the grommet itself and a means of setting it.

There are also dedicated grommet presses with punch and anvil, as shown in the picture, ranging from inexpensive to better-quality tools, which are somewhat faster to use.

[6] Grommets are generally used whenever wires pass through punched or drilled sheet metal or plastic casings for this reason.

These are called strain relief bushings and are often used to insulate, anchor, and protect power cords where they enter panels.

Grommets are used in a similar way to acoustically isolate electronic circuit components that are susceptible to microphonism caused by mechanical vibration or jarring.

In chronic cases of otitis media with effusions present for months, surgery is sometimes performed to insert a grommet, called a "tympanostomy tube" into the eardrum to allow air to pass through into the middle ear, and thus release any pressure buildup and help clear excess fluid within.

This is also a correcting measure for a patulous Eustachian tube (when air moves to and from the middle ear with each breath making the eardrum flap).