Code 61 and Code 62 4-Bolt Flanges (SAE J518)
This connection is commonly used to connect larger sizes of hose and tubing (3/4" to 3") in fluid power systems. An o-ring, inserted into a ring groove in the flange head seals on a smooth face female port and is held in place by two clamp halves (or a one piece clamp) which are held tight by four bolts located in a rectangular pattern.
J518 flanges come in two pressure classes. The standard series, Code 61 which goes to 3000 psi and the high pressure series, Code 62, where all the sizes are rated at 6,000 psi. J518 is interchangeable with ISO 6141, DIN 20066 and JIS B 8363, except for the bolt sizes.