Resistant to harsh chemicals and high temperatures, these balls stand up in applications as extreme as aerospace fuel systems. You can use them as seals in check valves and pumps or bounce them in vibrating sifters to clean screens. Made of Viton® fluoroelastomer rubber, also known as FKM, these rubber balls resist chemicals such as nitric acid, ethylene glycol, and isopropyl alcohol. Compared to Aflas, this rubber has better resistance to solvents and petroleum-based fuels. However, it doesn't hold up as well to steam and strong acids as Aflas.