ESI Super Cap Seal XL truck cap seal 20 ft — 2 1/8" x 1/2" EPDM for extra-wide rails, heavy-cap vibration damping

ESI Super Cap Seal XL is a heavy-duty 20-foot EPDM rubber seal specially shaped to mount truck caps or camper shells with extra-wide bed rails and weights over 200 lb.

This full-length seal is engineered for long-term automotive use, providing a durable, vibration-damping barrier between your truck bed rails and a bulky cap or shell. The kit arrives ready to install with adhesive butyl tape, alcohol prep wipes, and step-by-step instructions so you can fit a secure gasket without scavenging parts. Made in the USA from automotive-grade EPDM, the material resists compression set and stays flexible through temperature swings better than ordinary foam or PVC alternatives.

How will the Super Cap Seal XL fit my extra-wide bed rails?

The profile measures 2 1/8 inches wide by 1/2 inch high and comes as a continuous 20-foot length designed for full 8-foot bed coverage for wider rails and heavier caps. Because the seal is larger than standard seals, it fills oversized gaps and creates a consistent contact surface along the entire rail.

• Dimensions: 2 1/8" width × 1/2" height × 20' length
• Extra capacity to accommodate rails and boots wider than stock seals
• Continuous length avoids seams across the bed rail
• Trim or overlap for short beds when necessary

What makes EPDM better than foam or PVC seals for heavy caps?

Automotive-grade EPDM offers superior elasticity and long-term recovery after compression, so the seal maintains contact without permanently flattening. It also excels at damping vibrations from a heavy cap, reducing rattles and movement while driving.

• High compression-set resistance for longer sealing life
• Flexible across hot and cold temperatures without cracking
• Durable against repeated cap removal and reinstallation
• Preferred by installers for professional-grade performance

How easy is the Super Cap Seal XL to install and maintain?

Installation requires no special tools: clean the rail, apply the included butyl tape, and press the EPDM gasket into place following the supplied instructions. The seal won’t need replacement each time you remove the cap, so routine maintenance is minimal—periodic inspection and cleaning are usually sufficient.

• Includes butyl adhesive tape and alcohol pads for prep
• Step-by-step printed instructions for straightforward fitment
• Reusable between cap installations when handled properly
• Simple trimming if a slightly shorter length is required

Will this seal work for caps over 200 pounds?

Yes — the XL profile and robust EPDM compound were selected to support heavier caps and camper shells by providing a stable, compressive interface. The material’s resilience helps distribute loads while maintaining a weather-resistant barrier.

• Designed specifically with heavy caps and shells in mind
• Absorbs vibration to minimize wear and noise
• Maintains a consistent seal under significant weight
• Quality construction intended for professional installation use

Who this is for: The ESI Super Cap Seal XL is aimed at truck owners and professional installers who mount larger-than-stock caps or camper shells that exceed 200 pounds on extra-wide bed rails. It’s ideal if you want a durable, low-maintenance gasket that holds up to repeated use, harsh weather, and the stresses of a heavy topper—without the quick deterioration common to foam or PVC seals.