Pressure ratings for API 6A seals are classified by working pressure levels designated as 2,000 psi, 3,000 psi, 5,000 psi, 10,000 psi, 15,000 psi, and 20,000 psi. Each pressure class requires specific seal designs, materials, and testing protocols https://globalsealstech.com/product-category/oil-gas-seals/api-6a-wellhead-equipment-seals/