Simple, light, attractive... just a few of the reasons why this 1-5/16" threaded Spidertrax Filler Cap assembly is a great solution for custom off-road builds. Our Spider engraved 6061T6 billet aluminum filler cap has an o-ring seal to keep oil where it belongs and keeps the filler cap from loosening up. In addition, our double anodize protection will keep your filler cap from corroding even in the harshest terrain. Our weld-in steel sleeve has a large 1-5/16" diameter opening making filling easy. Our Spidertrax Axle Filler Assembly Kit contains one steel sleeve, aluminum cap, and o-ring.