This SAE Recommended Practice has been formulated to advance and endorse the use of the ISO (International Organization for standardization) Solid Contaminant Code as the universal means for expressing the level of particulate contaminant in hydraulic fluid and for specifying acceptable limits of cleanliness. Worldwide approval was gained for this coding system because it provides a simple, unmistakable, meaningful, and consistent means of communication between suppliers and users. The code applies to all types of hydraulic (liquid) fluids used in fluid power and control systems as applied to self-propelled machines as referenced in J1116. The purpose of this recommended practice is to provide a practical and uniform method for graphically representing the contamination level of a fluid and assigning its proper ISO cleanliness code. Although the approval code is explicit and offers no opportunity for misinterpretation, flexibility in application is provided to satisfy the customs of the cooperating nations. This practice is intended to facilitate the use of the ISO code and encourage its promulgation throughout the industry.