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 higher tensile strength while resisting corrosion.Many import fittings use lower quality brass with lower copper content, resulting in 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 generally comply with SAE, ASA, ASME, and MS standards. However, when design makes dimension 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 sizes listed are OD. To determine nominal size, subtract 1/8". Pipe sizes listed are standard nominal pipe size and threads are to dryseal taper pipe standards. JB will provide flare fitting to SAE standard J513 whenever possible. In some cases, slight deviations will occur when full compliance fittings are not available. Our tube fittings are make and break, have good vibration resistance, economical, easy to assemble, and are avialbe in a wide variety. Made in the USA.