Seals are the key components of hydraulic cylinders, hydraulic components, rotating shafts and related mating parts. The quality of seals is related to the normal operation and service life of the whole set of equipment. Therefore, how to correctly understand and select seals is crucial for users. Therefore, we have made this set of seals manual based on years of experience in sealing applications. The manual of O-ring and star ring seals mainly introduces and collects O-ring, star ring, backup ring, combined washer and ED washer.