4″This 1/4″ thick anodized aluminum plate with tapped holes from YakAttack is used for for strong installation ofGT90,GTTL90, andGTSL90GearTrac. Requires 1/2″ X 4″ flat area inside hull.GT90, GTTL90, GTSL90 backing plateSingle pack4″ longMade in the USA8″This 1/4″ thick anodized aluminum plate with tapped holes from YakAttack is used for strong installation ofGT90,GTTL90GTSL90GearTrac. Requires 1/2″ X 8″ flat area inside hull.GT90, GTTL90, GTSL90 backing plateSingle pack8″ longMade in the USA12″This 1/4″ thick anodized aluminum plate with tapped holes from YakAttack is used for strong installation ofGT90,GTTL90,GTSL90GearTrac. Requires 1/2″ X 12″ flat area inside hull.GT90, GTTL90, GTSL90 backing plateSingle pack12″ longMade in the USA