4LIFETIMELINES Copper Steel brake lines are manufactured from low carbon, roll-formed steel and a copper brazed bonding process. This makes for an extremely durable line that's easy to bend and form new lines from. The lines are then finished with an electric zinc plating and a copper plating for extreme protection against rust and corrosion, in even the harshest conditions. OD (3/16 inch, 4.76mm), Burst Pressure (12,599 psi), Working Pressure (3,400 psi), SAE J527, ISO 13486 4038, ASTM A254, Tensile Strength (42,050 psi, 290 MPa), Wall Thickness (0.028 inch, 0.70 mm). The SAE fitting pack in this kit is made up of the most popular and commonly used SAE fittings for 3/16 inch brake line replacement applications. All fittings meet and surpass SAE standards and are manufactured from high quality steel. Working temperature (Pressure) for our tube nuts are -65 degrees Fahrenheit to 250 degrees Fahrenheit.