JB machines all of the brass fittings at the factory in Aurora, Illinois using the highest level of brass, consisting of 65% copper and 35% zinc. This gives our brass fittings and access valves high tensile strength while resisting corrosion. Many import fittings use lower quality brass with lower copper content and higher failure rates. Our brass fittings may be used with copper, brass, aluminum, steel, and plastic tube provided an acceptable flare could be generated with the material. Vacuum pressures of 5,000 psi can be handled depending on the size, material, and conditions. Using a 4:1 safety factor, the following general rule is used: 3,000 psi to 1/4", 2,000 psi to 1/2", and 1,500 psi to 1". Long nuts are recommended when vibration is a factor. Tubing should be double flared in extreme applications to minimize flare thinning on over-tightening. Our brass fittings general comply with SAE, ASA, ASME, and MS standards. However, when design make dimensions critical, please contact us at 800-323-0811. heavy duty ACR tube fittings generally conform to SAE, ASA and ARI standards for marine, hydraulic, and refrigeration service. Long dryseal pipe threads minimize leakage and provide more clearance for tightening flare nuts. Shapes, elbows, tees, etc. are made from forged brass to maximize strength and eliminate cracks. Tube size listed are OD. To determine nominal size, subtract 1/8". Pipe sizes listed are standard J513 whenever possible. In some cases, slight deviations will occur when full compliance fittings are not available. Our tube fittings are make and brake, have good vibration resistance, economical, easy to assemble and are available in a wide variety.