Edge trim protects exposed edges and the people who come into contact with them. Trim seals, as edge trim is sometimes called, also provides a finished appearance to surfaces such as the doors on vehicles, machinery, and equipment. Choosing the right edge trim is important, but you’ll also need to install trim seals with care. Otherwise, these rubber or plastic products can buckle or separate.

In this guide from Elasto Proxy, you’ll learn how to select edge trim based on dimensions, materials of construction, and other application requirements. You’ll also learn some best practices for cutting and installing trim seals.

Edge Trim Dimensions

Selecting the right edge trim starts with measuring the thickness of the edge to cover. Your trim seal needs to have the same thickness as the edge. In other words, don’t select edge trim that’s too thick or too thin for the flange. For example, if you need to cover an edge that’s 0.125” (0.3175 cm) thick, choose a trim seal with an edge thickness of 0.125” (0.3175 cm) – not 0.120” (0.3048 cm) or 0.130” (0.3302 cm).

You’ll need to specify the proper leg length, too. As a rule, shallower flanges require shorter leg lengths. Longer flanges need longer legs. If the edge you need to cover is curved, measure the bend radius. Then compare this dimension to the minimum bend radius for the edge trim you’re considering. Remember that if your edge trim can’t accommodate the radius, the trim seal may buckle and fail.

Edge Trim Materials

Choose an edge trim material that can withstand the application environment and resist compression set, the permanent deformation of a material. Standard edge trim comes in these and other compounds.


Remains flexible at low temperatures and resists moisture and ultraviolet (UV) light. Fire-rated EPDM is available that meets flame, smoke, and toxicity (FST) requirements for buses, trains, and other mass transit applications.


Provides flame and water resistance but has more limited flexibility at low temperatures.


Strong, lightweight, and abrasion-resistant. PVC installs easily but may crack in the cold and fade in the sunlight.


Less likely to crack in the cold than PVC but more expensive than other edge trim materials, including EPDM. Supports recycling.


Provides low toxicity, low chemical reactivity, and thermal stability over a wide temperature range. Dust may adhere to silicone, however. 

Edge trim can be made of solid, sponge, or dual durometer rubber. Harder rubber has a higher durometer and is more resistant to compression set. Bulb trim, a type of edge trim, can have a lower durometer bulb that supports compression and a higher durometer retainer that’s pressed into place over the flange and resists impact.

Most edge trim is black, but you can choose trim seals in colors such as silver or white to match your larger product designs. Edge trim can have a smooth or textured (pebbled) finish, too. For additional gripping, edge trim can have interior tongues. To help absorb impact, edge trim can contain steel wire or segmented steel cores.

  • Steel wires are spaced apart and run parallel to the length of the legs.
  • Segmented steel cores have sections that cover more surface area.

Because of steel’s ability to withstand impact under colder temperatures, you may need edge trim with a steel core for outdoor applications such the door seals on forestry or mining equipment.

Cutting Trim Seals

Edge trim comes in lengths that you can cut yourself. You can also buy edge trim that’s been cut-to-size and features smooth, clean edges. Cutting rubber in-house might seem cost-effective but using a hand tool like a wire cutter can crimp the ends and create material waste. Guillotine cutting also puts pressure on the profile. For best results, ask for trim seals that are cut with water jet equipment.

Abrasive water jet cutting is used with edge trim that contains steel wire or segmented steel cores. Creating mitered corners by hand can be difficult, but abrasive water jet cutting creates high-quality cuts every time. Often, these cuts are made at 45° angles into the face of the trim seal. By achieving uniform mating lines, complementary cuts can be joined together into finished gaskets.

If you still decide to make the cuts by hand, remember to feel for the gap between the clips if the trim seal has a segmented core. Otherwise, the edge trim may crush and deform if you don’t find the right spot before cutting. Also, it’s better to use a 90° miter tool rather than tin snips. Cut a notch from each leg but cut only one leg at a time.

Installing Trim Seals

Installing edge trim involves pressing the trim seal over the flange.  For best results, always install lengths of edge trim so that the ends won’t separate. Push the ends together and leave some material in the loop that’s created. Then push down on the edge trim to ensure a proper fit and avoid stretching. For high volume installations, you may want to use a pneumatic air hammer instead of your hands.

Would you like to learn more about edge trim dimensions, materials, cutting, or installation? Elasto Proxy keeps hundreds of standard profiles in stock and uses abrasive water jet cutting equipment for edge trim with metal cores. Please contact us for more information.  

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