The skeleton oil seal is a typical representative of the oil seal. Generally speaking, the oil seal means the skeleton oil seal. The function of the oil seal is to separate the lubricating parts from the output parts, so as not to let the lubricating oil leak. The skeleton acts as a reinforcing bar in the concrete member, reinforcing the shape and tension of the oil seal. It can be divided into single lip skeleton oil seal and double lip skeleton oil seal according to the structure. The lip of the double lip seal prevents dust and impurities from entering the machine. According to the skeleton type, it can be divided into inner shell skeleton oil seal, exposed skeleton oil seal and assembly type oil seal. According to the working conditions can be divided into rotating skeleton oil seal and reciprocating skeleton oil seal. For gasoline engine crankshaft, diesel engine crankshaft, transmission, differential, shock absorber, engine, axle and other parts.