The ST Series hub caps from Valcrum feature an aluminum alloy body designed to resist cracking that is suited for grease and oil bath applications. Each hub cap includes an oil level indicating window as well as a magnetic vent plug to remove metallic particles, as well as an easy to access drain/fill port. The universal threaded hub caps come in a variety of sizes from 2-7/8" to 4" and can fit 6K-16K axles.