Packer elements are the most recognizable downhole seals. They consist of a central rubber section bonded to metal end rings. When set by compression, hydraulic pressure, or swelling, the rubber extrudes radially against the casing or borehole wall, creating a high-pressure seal capable of holding thousands of psi differential. https://globalsealstech.com/product-category/oil-gas-seals/downhole-completion-tools-seals/