The skeleton oil seal is a typical representative of the oil seal. Generally speaking, the oil seal refers to the skeleton oil seal. The function of the oil seal is generally to isolate the parts that need to be lubricated in the transmission parts from the external environment, so as not to let the lubricating oil leak. The skeleton is like the steel bars in the concrete member, which acts as a reinforcement and enables the oil seal to maintain its shape and tension. According to the structure, it can be divided into single lip skeleton oil seal and double lip skeleton oil seal. The auxiliary lip of the double-lip skeleton oil seal plays a dust-proof role to prevent external dust and impurities from entering the machine. According to the skeleton type, it can be divided into inner skeleton oil seal, exposed skeleton oil seal and assembled oil seal. According to working conditions, it can be divided into rotary skeleton oil seal and reciprocating skeleton oil seal. For gasoline engine crankshafts, diesel engine crankshafts, gearboxes, differentials, shock absorbers, engines, axles and other parts.