These items have come out of storage. There are various sizes and thicknesses. I don't know what they're used for, but I'm putting them up for sale. Please understand that I can only answer questions to the best of my knowledge. ※AI Summary The image shows O-rings of various sizes. O-rings are circular (O-shaped) mechanical parts with a circular cross-section, mainly used for sealing gases and liquids. Applications: Used to prevent fluids from entering equipment and to prevent internal fluids from leaking out. Material: Generally made of rubber. Function: They are installed in grooves and seal fluids such as oil, water, air, and gas by the repulsive force generated by moderate compression. Features: The simple shape makes them easy to install and highly versatile. Please check the photos and purchase if you understand that these are used items. They will be shipped in simple packaging.