EPDM sponge rubber double bulb seal with premium 3M Peel-N-Stick adhesive backing. Designed for truck caps, tonneau covers, and hard top bed covers. A great upgrade over original factory seals — wider double bulb profile provides coverage across bed rail gaps that a single bulb cannot span. Just peel, press, and seal. Hand crafted and made in USA.
The Steele Rubber Products 90-3520-283 is a 1/2" high by 1-9/16" wide EPDM sponge rubber double bulb extrusion with premium 3M Peel-N-Stick adhesive backing. The double bulb profile spans 1-9/16" across the truck bed rail flange, with the two parallel bulbs set 1/2" apart. When the truck cap or tonneau cover is lowered onto the bed, both bulbs compress simultaneously against the mounting surface, distributing clamping load evenly across the full width of the seal and creating two parallel lines of weathertight contact. This dual-contact geometry seals out rain, wind, road dust, and exhaust fumes from entering the truck bed more reliably than a single bulb or flat foam profile of equivalent height.
This seal is a direct upgrade over the original seals found on truck caps and tonneau covers. Original factory seals are typically thin foam or single-profile rubber that compresses flat with age, loses sealing depth, and eventually allows water to track in along the bed rail. The Steele Rubber EPDM sponge construction will not permanently compress, fade, shrink, or crack — and the double bulb geometry maintains two effective sealing lines even as the material ages. At 30 ft, this strip is sufficient for a complete seal replacement on standard short-bed and long-bed trucks with a typical truck cap perimeter. Available by the foot and in 15 ft and 30 ft pre-cut lengths.
Two parallel EPDM sponge bulbs set 1/2" apart span the 1-9/16" seal width — two simultaneous lines of weathertight contact against the truck cap or tonneau cover mounting surface
Factory-bonded 3M adhesive backing provides strong, long-lasting grip on truck bed rail flanges — no additional adhesives or tools required for standard installations
A great upgrade from original truck cap and tonneau cover seals that compress flat and lose sealing depth over time — EPDM sponge rubber maintains its shape and sealing performance
Weather-resistant EPDM sponge rubber resists moisture, ozone, and UV exposure — will not fade, shrink, or crack through years of outdoor truck use and seasonal temperature cycling
The 90-3520-283 is a universal application seal — no specific truck make or model fitment list is available. It is selected by profile measurement and bed rail flange geometry rather than by vehicle year, make, or model. Designed For: • Truck Caps (Camper Shells): Replacement seal for the perimeter base rail of fiberglass or aluminum truck caps where the original seal has compressed flat, hardened, or pulled away from the bed rail • Tonneau Covers: Replacement or upgrade seal for folding, rolling, or hard tonneau covers where the perimeter seal contacts the bed rail flange • Hard Top Bed Covers: Universal fit for one-piece or hinged hard bed covers requiring a resilient double bulb perimeter seal • General Bed Rail Sealing: Any truck bed application where a 1/2" H x 1-9/16" W double bulb profile with adhesive backing is the appropriate replacement How to Confirm Correct Fit: Measure the width and height of the existing seal or the mounting flange gap your truck cap sits on. This seal measures 1/2" H x 1-9/16" W with 1/2" spacing between the two bulbs. If your existing seal matches these dimensions, the 90-3520-283 is the correct replacement. If the existing seal is narrower (single bulb) or significantly taller, a different profile may be required.
Proper surface preparation and application temperature are critical to achieving a lasting 3M adhesive bond: • Clean thoroughly before applying: Remove all old adhesive residue, dirt, oil, wax, and moisture from the bed rail flange. Use isopropyl alcohol or equivalent surface cleaner and allow to dry completely • Application temperature: Apply only when both the seal and the bonding surface are between 60°F and 104°F (15°C and 40°C). Cold surfaces below 60°F will significantly reduce initial adhesive tack • Match surface temperatures: The temperature difference between the seal and the bonding surface should be as small as possible for maximum adhesion • Press firmly along full length: After positioning, press the seal base firmly along its entire length to maximize adhesive contact with the flange surface • Cure before clamping: Allow the adhesive bond to develop for several hours before installing the truck cap or tonneau cover and applying compression load • Measure and cut before peeling: Cut each run to length before removing the release liner — repositioning after adhesive contacts the surface weakens the bond
Step-by-Step Installation: 1. Remove the Old Seal: Lift away the existing truck cap or tonneau cover to access the bed rail flange. Peel off the old seal. Use a plastic scraper to remove remaining adhesive residue without scratching the bed rail 2. Clean the Bed Rail Flange: Wipe thoroughly with isopropyl alcohol. Remove all oil, wax, dirt, and moisture. Allow to dry fully before proceeding 3. Check Temperature: Confirm both the seal and the bed rail surface are between 60°F and 104°F. Do not install in cold conditions — adhesive tack drops significantly below 60°F 4. Measure and Cut: Measure each side of the bed rail perimeter and cut the seal to length before peeling the liner. Miter corners at 45° for the cleanest fit at front and rear corners 5. Dry-Fit: Lay the cut strips along the bed rail without removing the liner to confirm length and corner alignment before committing to adhesive contact 6. Peel and Press: Starting at one corner, peel back a few inches of the release liner, align the seal centered on the bed rail flange, and press firmly as you progressively peel and apply along the full run 7. Press Full Length: Once all strips are in position, run a roller or firm thumb pressure along the entire length of each run to maximize adhesive contact 8. Allow Cure Time: Allow several hours for the adhesive bond to develop before reinstalling the truck cap or tonneau cover and applying compression load 9. Reinstall and Test: Lower the truck cap or cover back onto the bed. Check the seal compression along the full perimeter — both bulbs should compress evenly with no gaps or lifted sections
In The Package: • One (1) continuous 30 ft strip of 90-3520-283 EPDM Sponge Rubber Double Bulb Truck Cap Seal with 3M Peel-N-Stick Adhesive Also Available In (Sold Separately): • Same profile, by the foot — for individual section replacement or profile verification before purchasing a full-length strip • Same profile, 15 Ft strip — for short-bed trucks or partial replacement jobs Recommended Tools (Not Included): • Isopropyl alcohol and clean cloths for surface preparation • Plastic scraper for old adhesive removal • Sharp utility knife or scissors for cutting to length • Tape measure • Hand roller or firm thumb pressure for adhesive seating
A single bulb seal concentrates all sealing contact on one narrow line of compression. If the truck cap or tonneau cover mounting flange has minor warps, surface irregularities, or inconsistent clamping pressure, the single bulb can lift away from the flange in those sections — creating gaps where water and wind enter the bed. The double bulb geometry changes this dynamic in two important ways: • Redundant sealing lines: Two parallel bulbs create two independent compression contacts across the full perimeter. Even if one bulb has a minor gap at a flange irregularity, the second bulb provides a backup seal at the same location • Wider coverage footprint: The 1-9/16" overall width bridges across bed rail flanges and minor surface steps that a narrow single bulb profile cannot span without leaving exposed gaps at the edges The result is a more forgiving and consistently weathertight seal across the variety of truck bed rail geometries found on different truck makes, bed lengths, and cap mounting configurations. This is why double bulb profiles are the preferred upgrade over original single-profile factory seals.
The double bulb EPDM design directly addresses the two most common reasons truck cap seals fail: permanent compression set that eliminates sealing depth, and a single narrow contact line that cannot accommodate minor bed rail irregularities. Replacing a degraded factory seal with the 90-3520-283 restores a weathertight bed enclosure and extends the service interval significantly compared to replacing with an equivalent foam or low-grade rubber seal.