Please measure the diameter of your current fuel cap or fuel tank fill tube prior to ordering. One 3 1/2” 5.5 TPI NS Locking, aluminum, diesel fuel cap. Female fitting, for diesel application only. For use on thermally vented fuel tanks. Supplied with 2 matching keys (keys are not available separately). Utilizes a Viton O-ring for superior resistance against shrinking and cracking Stainless steel retaining chain and bail for corrosion protection Approximate dimensions = Across threads cap 3 7/16”, Across threads filler neck 3 1/2” Approximate net weight = 11 oz