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Perma-Fit™ Cargo Door Seals

To purchase please contact your local RV Dealer.

Perma-Fit is an advanced technology, non-cellular thermoplastic vulcanate (TPV) now available in clip bulb seals for cargo doors and other places where such seals are appropriate.

Seal Design cargo door seals are a one-piece bulb and clip co-extrusion rather than separate clip and bulb components glued together. This results in an automotive grade seal that’s virtually indestructible for the life of the doors.

TPV seals also offer a much more durable option than EPDM bulb seals, which are often over compressed by manufacturers seeking a tighter seal. The open cell structure of EPDM seals is not made to be compressed more than 30 percent, but manufacturers often compress the seal by as much as 70 percent. In this case, the open cell structure of EPDM seals will quickly break down, causing the seal to fail, with leaking the likely consequence. The seals can also shrink and become brittle.


Most cargo doors utilize clip bulb seals, which require a co-extrusion consisting of a bulb portion and the clip section. These co-extrusions can be made in one of two ways:

A. As a two-piece extrusion where the bulb and clip are manufactured separately and then glued together.

B. As a one-piece extrusion where both bulb and clip are extruded together as one piece.

All Perma-Fit cargo door seals have a one-piece extrusion which is much more durable and will last far longer than the two-piece alternative commonly used in the RV industry. The automotive industry uses 100 percent one-piece co-extrusions because of the dependable quality of one-piece TPV bulb material and because TPV has proven to be extremely durable and high quality, working for automotive applications as well after 20 years as they do on day one. Perma-Fit is the only single-piece bulb co-extrusion of this kind for cargo door and RV use.


EPDM extrusions are cellular in nature with small pockets of air in the rubber. Over time, the cells break down (burst) and the pocket collapses thereby losing it's "bouce back" capabilities. Permanent compression results, the seal is compromised and leaking is the likely consequence.



Used by all automobile companies for door seals, thermoplastics have no cells, there are no pockets of air to collapse and compression set will never take place. As a result, Perma-Fit extrusions will seal as well after 20 years as they do day one.


In addition, the TPV bulb seals can be compressed up to 70 percent and still hold up for the life of the cargo door. TPV has no cell structure that can break down. Since there are no air pockets to collapse, compression set will never take place and the seal will bounce back without compromise. As a result, Perma-Fit bulb seals are more elastic and durable and perform well for a long time.

Many bulb profiles are available. Contact Seal Design with your specs or goals. We can also design any seal and create tooling as needed for your specialty sealing needs.

More Features and benefits of TPV extrusions

Feature Benefit
Excellent ozone, water and temperature resistance. Maintains performance no matter what the climate or weather situation.
Will not chalk with UV exposure Maintains attractive apparence over time.
Energy Star, AAMA tested, approved and rated. Assures energy efficiency and that it's harmless to the environment.
Manufactured under TS16949/ISO 9000 automotive certifications. Will not out-gas or chalk and is much cleaner for the environment.


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Seal Design and Dicor Corporation focus on the people and companies that use our products. This includes products, support and services that help improve the production process.

  • Perma-Fit bulb seals require no significant changes in the manufacturer’s production process to use. The material is also recyclable, yielding overall part cost reductions.
  • Only one supplier source needed, even if using several different profiles.
  • Manufacturers can benefit from overall part cost reductions because of recyclability. There’s no production line stoppage because product has indefinite shelf life.
  • Seal Design will audit the extrusion needs of customers to identify potential cost savings, installation improvements, and problem solving solutions. Plus we will conduct cycle counts and help with inventory management.