Oil seals, also known as rotary shaft seals or lip seals, serve the primary function of sealing the rotating shafts in mechanical systems. They are typically made from elastomers, metals, or a combination of both, offering good resistance to various fluids, including oils, greases, and water. The 50x90x10 oil seal, with its dimensions indicating a 50mm inner diameter, 90mm outer diameter, and a width of 10mm, is designed to fit specific shaft sizes while providing optimal sealing performance.