In fluid power systems, power is transmitted and controlled through a fluid (liquid or gas) under pressure within an enclosed circuit. Components must be designed to meet these requirements under varying conditions. Testing of components to meet performance requirement provides users a basis of assurance for determining design application and for checking component compliance with their stated requirements.

ISO 3601-3:2005 lays down the quality acceptance criteria of O-rings used in fluid systems, the dimensions of which are standardized in ISO 3601-1, ISO 16031-1 and ISO 16031-2.

ISO 3601-3:20051 also defines and classifies surface imperfections on O-rings and specifies maximum acceptable limits for these imperfections.

ISO 3601-3:2005 is also applicable to O-rings to be used in aerospace construction.