Performance specification levels (PSL) in API 6A establish increasingly stringent quality and testing requirements, with PSL 1 through PSL 4 representing progressively higher quality standards. Higher PSL ratings require additional material testing, dimensional verification, and performance validation, with PSL 3 and PSL 4 reserved for critical applications where seal failure conseque... https://globalsealstech.com/product-category/oil-gas-seals/api-6a-wellhead-equipment-seals/