Sealing products are divided into three categories: O-rings, skeleton oil seals and sealing strips. O-rings and skeleton oil seals are installed in the engine, gearbox, car main shaft and hydraulic pneumatic transmission system to prevent leakage of lubricating oil, hydraulic oil and other liquids or gas leakage, to ensure the normal operation of various component systems, and to prevent external sand dust and impurities from entering the system and affecting the normal operation of the machine. O-rings and skeleton oil seals are primarily used for the sealing of rotating shafts or reciprocating shafting. According to the structure, the skeleton oil seals can be divided into inner skeleton oil seals, outer skeleton oil seals, semi-exposed skeleton oil seals, lip oil seals, sub-lip oil seals and combined oil seals; according to the installation parts in the car, they can be divided into crankshaft front oil seals, crankshaft rear oil seals, transmission oil seals, cam box oil seals, wheel housing oil seals, semi-shaft oil seals, pneumatic guide oil seals and shock absorber oil seals. Sealing strips are mainly used in automobile doors and windows, trunks, engine covers, etc., functioning as sealing, windshield, rainproof, shock absorption and sound insulation. According to the structure, they can be divided into pure rubber sealing strips (also can be divided into sponge rubber and dense rubber) and composite sealing strips (can be divided into rubbers/metal skeleton composite strips, two or more rubber composite strips and rubber-plastic composite strips).