A rubber oil seal, also called a "lip seal" or "shaft seal", is a circular component made primarily of rubber, designed to prevent leakage of oil or grease from a rotating shaft within a machine by creating a tight seal between the shaft and the housing, effectively keeping lubricant in and contaminants out; it typically consists of a flexible rubber lip that presses against the shaft, with a metal housing to hold it in place, and is commonly used in automotive, industrial, and machinery applications to maintain proper lubrication and prevent damage from dirt and debris.