The Dana 30 Diff cover is designed with pure function in mind. Like all of the Kryptonite Series Diff Covers the Dana 30 diff cover is fabricated with 1/4 inch steel plate for the cover and has 3/8 inch steel ring for the base. With a 3/8 inch thick steel ring the cover is built to resist "peel up" as you drag your diff over rocks and other terrain. The Dana 30 diff cover has a fill plug. The fill plugs have a cnc machined boss that extends out to protect the plug. All diff covers are shipped unpainted. All diff covers are shipped with new bolts and a fill plug for models that require one.