391 Fluorosilicone O-ring 70A Shore Blue, -12 Pack Fluorosilicone has very good resistance to ozone, weathering, detergent, salt water, engine and transmission oil, non-petroleum brake fluid, hydraulic fluids that resist fire, vegetable and animal oils, high molecular weight chlorinated aromatic hydrocarbons, and has better mineral oil, fuel, and aromatic hydrocarbons (benzene) compatibility than Fluorosilicone.