Copper Pigtail for Oxygen. The Amico copper pigtails shall have a 5/16” x 0.065” wall thickness, copper tube. The Amico copper pigtails shall come with a check valve equipped to one of the ends. Note: Burst pressure ratings for pigtails are determined at room temperature with the hose in a straight line. A safety factor of 4:1 or 5:1 should be used for normal applications. Impulse and shock pressure applications may require a higher safety factor. Note: Do not apply heat to pigtails. All cylinder connections machined to CGA specifications for applicable gases.