ESI Super Cap Seal XL EPDM Truck Cap Gasket, 23 ft Triple-Bulb 2 1/8" Wide — Weatherproof Vibration Dampening

ESI Super Cap Seal XL is a heavy-duty, 2 1/8"-wide EPDM triple-bulb gasket sized at 23 feet to seal truck caps weighing over 200 lbs and close large bed-rail gaps.

Built for professional installers and owners of heavyweight truck caps, this full-length gasket kit delivers durable weather sealing and vibration damping where standard foam or PVC seals fail. The Super Cap Seal XL provides a broad contact area thanks to its triple-bulb profile, arrives as a complete kit with adhesive and prep materials, and is manufactured in the U.S.A. to resist compression set and maintain performance through repeated cap removals.

How does this seal improve fit and reduce rattling?

The wider 2 1/8" triple-bulb design fills larger gaps along the bed rail, creating a more consistent contact surface between the cap and the truck bed. Its EPDM compound absorbs vibration better than foam, which reduces movement and noise under highway conditions. You’ll notice a firmer, quieter connection that holds up through repeated use.

• Triple-bulb profile increases surface contact for wide gaps.
• EPDM rubber resists compression set for long-term sealing.
• Reduces cap-to-bed vibration and rattling on rough roads.

Will this fit my truck bed and heavy cap?

The Super Cap Seal XL is supplied in a 23-foot length and measures 2 1/8" wide by 1/2" high, making it suitable for most full-size beds and caps over 200 lbs. If your bed is under eight feet long, a 20-foot version is recommended instead. The profile is easy to trim so you can achieve a custom fit on narrower front rails.

• Length: 23 feet; width: 2 1/8"; height: 1/2".
• Recommended for caps weighing more than 200 lbs.
• Trim-to-fit design for non-standard rail widths.

What comes in the kit and how difficult is installation?

The kit includes the full-length EPDM seal, butyl tape for adhesion, alcohol prep pads, and step-by-step instructions to guide a professional or experienced DIY installer. Installation is straightforward when the rail is cleaned and prepped; the supplied butyl tape provides a reliable initial hold while the seal compresses into place.

• Complete kit: seal, butyl tape, alcohol pads, instructions.
• Prepare rails with supplied alcohol pads for best adhesion.
• Designed for professional installers but accessible to careful DIYers.

How durable is EPDM compared with foam or PVC seals?

EPDM is selected for its resistance to weathering, ozone, and repeated compression — properties that outlast many foam and PVC alternatives. The material’s superior compression set resistance means it maintains sealing force over time, so you won’t need to replace it every time the cap is removed. That longevity is why installers prefer EPDM for heavy caps.

• Long service life with excellent weather and ozone resistance.
• Maintains sealing integrity after repeated compressions.
• Preferred by professional installers for heavy-duty applications.

Who is this for: The Super Cap Seal XL is aimed at truck owners with heavyweight caps, fleet operators, and professional top manufacturers or installers who need a robust, long-lasting gasket. If you want a wide-profile EPDM seal that fills large gaps, reduces noise, and withstands repeated cap removals, this kit provides a ready-to-install solution with materials and instructions tailored for dependable, professional-grade results.