Super moisture barrier double bulb seal prevents dust, fumes and water from invading the interior of a truck bed. Easily trims in half to fit trucks with smaller width front bed rails. NOTE: To determine if you need to use a Front Rail Seal 6ft (ASIN: B00C0WVV72) measure the difference in height from the truck's side bed rails (including, if any, bed rail caps) to the truck's front bed rail. If the height of the gap is .250" or less install Super Cap Seal only. If the height of the gap is from .251" to .487" install Front Rail Seal on the cap's front base rail and install Super Cap Seal on the cap's side base rails. If the height of the gap is extra large, from .488" to .875" install Super Cap Seal on the cap's front and side base rails and install Front Rail Seal on the truck's front bed rail. OTHER QUALITY TRUCK CAP SEALS FROM ESI: 1 1/2" wide Ultra Cap Seal 23ft (ASIN: B00MPMBIZW) fills all bed rail gaps, for caps over 200 lbs. IMPORTANT: To completely seal out dust, fumes and water install an Ultimate Tailgate Seal with Taper Seal to the tailgate gap and sidewalls (ASIN: B00IPQWXZQ). MADE IN USA