Oil seals often called as grease, fluid or dirt seals have close spaces between stationary and moving components in mechanical equipment, helping prevent lubricant escape. They also stop harmful contaminants from entering machinery, particularly in severe environments. Vital components of practically every type of machine and vehicle in operation, oil seals protect all types of precision-constructed, close-fitting ball, sleeve and roller bearings. In precision bearings, oil seals help prevent lubricants from escaping the bearings or a specific area. In machine components, oil seals help prevent abrasives, corrosive moisture and other harmful contaminants from entering machinery. They also help stop intermixture of two different mediums, such as lubricating oil and water. Timken® National® Oil Seal, Single-Lip, Series: 350000, 2-1/2 in Inside Dia, 4.26 in Outside Dia, 60 to 80 Durometer, 1/2 in Width, Type 35 Cross Section, -40 to 225 °F, Nitrile Lip, Domestic