TC stands for skeleton oil seal, that is, inner skeleton, with rubber outside and iron inside.
Oil seal is the customary name of general seal, which is simply the seal of lubricating oil.
Oil seals are generally divided into single type and assembled type. Assembly type means that the frame and lip materials can be freely combined, which is generally used for special oil seals.
As the name implies, oil seal is a mechanical element used to seal oil (oil is the most common liquid substance in transmission system, and also refers to the general liquid substance). It separates the parts that need lubrication in the transmission part from the output part, so as to prevent the lubricating oil from leaking.