Hydraulic hose construction and performance is covered by various national and international standards including ISO, BSI, SAE, DIN, API, and CETOP. Most proprietary hoses conform to one standard or another, the SAE standards being the most widely followed in the U.S. SAE standards provide general, dimensional, and performance specifications for the most common hoses used in hydraulic systems on mobile and stationary equipment.
For decades, SAE J517 has published guidelines for 100R1 through 100R12 series hydraulic hoses. These manufacturer-driven SAE standards have been based on design, construction, and pressure ratings to ensure that hydraulic hoses meet minimum construction requirements. SAE established minimum pressure ratings for various hoses (inside diameters and were later revised to also include constant-pressure hoses, which are hoses that maintain pressure ratings within a group regardless of size). Some common constant-pressure hoses are R13, R15, R17 and R19.
Read more: Making Sense of Hydraulic Hose Standards