Lightweight, super-strong composite resists impact damage, chemicals, corrosion from road salt, UV, and seals against flooded loading docks Hub cap kit Includes: oil window, black vent plug, slotted bolt hole gasket, 6 mounting bolts and magnetic side-fill plug Magnetic side-fill plug with O-ring provides extra leak protection and traps metal particles to protect seal and bearings Molded pressure ridge on flange surface bites into sealing gasket to ensure leak-proof fit Bolt holes = 6, bolt circle = 5.5”, bolt size = 5/16 Approximate dimensions: inner diameter = 4.44” outer diameter = 6.25”, height = 2.469”, axle extension = 1.73” Fit = trailer Replaces: SKF 1643, Stemco 343-4009 & 364-4009 (Defender)