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Rubber Grommet Sizes: Tips for Choosing Grommets for Your Automobile

What are some of the rubber grommet sizes? Join us in this guide as we bring you all the insights on these components. 

Electrical wiring in autos is a sensitive undertaking, meaning you must get things right. 

Otherwise, cuts on the wires from sharp edges where they pass through can lead to short circuits and power losses. 

Therefore, rubber grommets come in handy. In this guide, we will cover their uses, sizes, types, makeup materials, shapes, and anything critical about them.

What is a Rubber Grommet?

As their names suggest, these are rubber tubes/edges commonly used in electrical engineering to cover sharp and rough edges. 

Other common names for these components include bushings, eyelets, and edgings. 

Also, most are black, although you may encounter gray or transparent ones. 

Rubber Grommet Use

Driveshaft grommets. 

Driveshaft grommets. 

In automotive applications, grommets are useful in the main ways: 

  • First, they are handy in sealing hole edges where cables and wires pass through, preventing abrasions. 
  • Also, they shield the cables from snags and cuts. Their strain relief feature means they can significantly increase the use life of wires and cables. 
  • Thirdly, by covering the hole, rubber grommets prevent the contact with dust and provide high liquid ingress protection to the wires. 
  • They are also valuable for improving the aesthetic appearance of where they are used. The components enhance the electrical systems’ overall outlook by covering gaping holes. 
  • Finally, they also minimize vibrations, keeping the cables in place, thus preventing disconnections. 

Thanks to their exemplary features, rubber grommets are helpful in several industries. 

You’ll find them in automotive engineering, telecommunications applications, and internet data centers. 

Also, they are prevalent in most electronics. Lastly, you’ll find them in fields where high equipment dependability, such as the medical industry, is crucial. 

Why are Rubber Grommets Made of Rubber?

Black grommet waterproof rubbers. 

Black grommet waterproof rubbers. 

The resistance of rubber to most elements of nature is the cardinal reason it’s the material of choice in making grommets. It can withstand the following: 

  • Exposure to ultraviolet light (UV), heat, ozone, and all weather conditions.
  • Acids like Sulphuric acid, HCL, phosphoric acid, saltpeter, and alkalis. 
  • All forms of strain. 

Grommets are also rubber-made because they barely dry out while it’s also crack-proof. 

Also, inserting them is easy; they’re push-fit and need no adhesive or screwing to install. 

Rubber Grommet Types

Rubber Grommets/seals. 

Rubber Grommets/seals. 

Here are the common grommet types in your local electrical and hardware stores.

Open Rubber Grommets

They are the most basic types of rubber grommets. They are renowned for their hole at the center, which is useful in shielding the wires passing through from abrasion. 

Rubber Blanking Plugs

Their cardinal role is sealing holes in fixings where high pressure is prevalent because they can withstand high pressure from above or below. 

One principal variation of the rubber blanking plugs is the diaphragm grommet

Typically, the diaphragm grommets have a hole through which you can install a wire to tighten their grip. 

Stepped Rubber Grommets

Their standout property is the tapered cone shape and markings that indicate where you can cut them into small bits. 

Hence, they are the ideal grommets for applications with multiple cable sizes because they are customizable. 

Rubber Grommet Strips

They are the most unique grommets primarily because they are strips rather than round fixings. 

Place them on the sharp panel you want to cover to blunt its edge. Their upside over typical grommets is that you can cut these to the size you choose. 

Tapered Rubber Grommets

They feature a tapered design, making them ideal for the relatively thick panels. Hence, they are essential when you cannot use closed grommets. 

Custom Rubber Grommets

Depending on your specifications, you can also get grommets with a custom size and shape from the manufacturer. 

These custom rubber grommets/ special shape grommets are common in scenarios where custom designs are essential. 

White Rubber Grommets

We earlier highlighted that most grommets are black. So why are these white colored? 

It is because they are silicone-made. They are also specialty grommets suited to application with extreme temperatures. 

They can withstand temperatures between 55°C and 180°C. Also, special versions of these grommets can withstand extremely high temperatures of up to 800°C. 

Rubber Grommet Shapes

Two rubber grommets. 

Two rubber grommets. 

Grommet manufacturers make them in different shapes to suit the varying applications. 

Among the various configurations you’ll encounter in the market include the following: 

  • D-shaped rubber grommets
  • Oblong rubber grommets
  • Oval rubber grommets
  • Square rubber grommets
  • Round rubber grommets
  • Rectangular rubber cable grommets

Hence, you must choose the ideal shape for your application to ensure a perfect joint. 

Rubber grommet materials

Thermoplastics are some of the common high-quality rubber grommet materials. 

Thermoplastics are some of the common high-quality rubber grommet materials. 

The most common rubber grommet makeup materials are as follows: 

Also, other popular classifications of grommets based on their materials include: 

  • Nitrile rubber grommets
  • Neoprene grommets
  • Silicone grommets

Rubber Grommets Specifications

A mechanic repairing rubber grommets. 

A mechanic repairing rubber grommets. 

Their features vary depending on the individual grommets’ specific makeup materials. But the generic features for all grommets include: 

  • They are resistant to high heat exposure 
  • Secondly, they are essential in cushioning wires/cables from tears. And this explains their use around openings. 
  • Lastly, grommets are resistant to tears. 

Rubber Grommet Sizes

Grommets in Application. 

Grommets in Application. 

Before delving into the rubber grommet sizes, let’s first explore the main grommet metrics. 

  • Panel hole diameter represents the hole size through which you insert the grommet. 
  • Maximum cable diameter: This metric is relevant when deciding if the grommet is big enough to accommodate the cable/wire you want to pass through the grommet. It indicates the maximum cable thickness that can pass through the grommet.  
  • Maximum panel thickness: It is the maximum depth of the metal panel. The metric is vital in selecting the ideal grommet size to fit through it. 

Let’s now see the main available grommet sizes based on the above metrics: 

Panel Hole DiameterMaximum cable diameterMaximum panel thickness

Tools Used to Measure Rubber Grommets

Finding the proper fit grommet for a specific application requires using the right tools. These measurements are easy to take as long as you have the tools below: 


Digital calipers are handy in finding the precise diameters of the grommets. But you can still use a manual caliper, although you must have the requisite skills to take readings with the instrument. 


A digital micrometer. 

A digital micrometer. 

They are similar to calipers but are more precise and thus valuable for finding intricate details of the grommet dimensions. 

Depth Gauges

A Depth Gauge. 

A Depth Gauge. 

Do you want to determine the rubber grommet thickness to evaluate if it fits on the hole? A depth gauge is the ideal tool for this application. 


It tests the hardness levels of the rubber grommet. Thus, it’s an essential tool in high-pressure grommet applications where hardness immensely matters. 

How To Measure For Rubber Grommets Properly

Measuring diameter with a caliper. 

When finding the perfect fit component for a particular application, you must measure the grommet and the panel size. Here are the steps: 

Measure the Panel

  • Using a micrometer or a caliper, measure the panel thickness where you want to install the grommet. 
  • Next, measure the depth of the hole the grommet shall pass through. 
  • Now, test the side of the cable/cable you’d like to pass via the panel. 

Measure the Grommet

Using a caliper/micrometer, measure the grommet thickness, interior diameter, exterior diameter, and panel hole diameter. 

Tips on Choosing the Right Rubber Grommet

An insulation rubber grommet encases a pipe.

An insulation rubber grommet encases a pipe.

  • First, ensure you get the grommet size and panel thickness right. Ideally, the grommet diameter should be commensurate with the panel hole you’re looking to cover. 
  • Also, ensure you pick the suitable grommet rubber according to its application. It should be durable yet high-quality rubber. There are different rubber grades. Thus, the rubber grommet should best fit high-pressure and high-temperature range applications. 
  • It will also help to consult experts in rubber molding if you need custom-made best-fit rubber. 
  • Lastly, choose the appropriate automotive rubber grommet thickness. Again, your choice should be informed by the application. Grommets for use in intense environments should be highly thick.


Tight rubber grommets are as critical as wiring harnesses in car auto systems. Both play the role of insulating the current-carrying cables/wires from heat and pressure.

We have covered some of the critical considerations when choosing the ideal grommet. 

Pay attention to each and ensure you get the correct grommet grade for outstanding results. 

Most importantly, choose the ideal grommet thickness corresponding to the hole you’re covering. 

Hey, I am Lillian Yang, Sales manager of Cloom Tech.

I am a responsible, intelligent and experienced business professional with an extensive background in the electronics industry.

Reach me at [email protected] to get a quote for your projects.

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