For truck caps that require less than 23ft of seal use Super Cap Seal 20ft. 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 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 XL on the cap's front base rail and install Super Cap Seal 20ft on the cap's side base rails. If the height of the gap is extra large, from .488" to .875" install Super Cap Seal 20ft or 23ft 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: 2" wide Premium Cap Seal XL 23ft fills small to medium bed rail gaps, for caps that weigh 200 lbs or less. 2 1/8" wide Super Cap Seal XL 23ft is for trucks with extra wide bed rails, fills all bed rail gaps, for caps over 200 lbs. 1 1/2" wide Ultra Cap Seal 23ft fills all bed rail gaps, for caps over 200 lbs. IMPORTANT: To completely seal out the elements install an Ultimate Tailgate Seal with Taper SealĀ® to the tailgate gap and sidewalls. Save 25% and buy the COMBO Pack: Super Cap Seal 23ft and Ultimate Tailgate Seal with Taper SealĀ®. MADE IN USA