The flexible inner core is made from a spiral wound strip of heavy gauge, corrosion resistant, hot dipped galvanized steel. The 3/8 through 1-1/4 in trade sizes are squarelock formed and include an integral bonding strip of copper that is enclosed within the convolutions throughout their entire length. The 1-1/2 through 4 in trade sizes are designed with a fully interlocked strip. The liquidtight jacketing material is of a high quality, rugged, flame retardant flexible PVC compound that resists oils, mild acids and exposure to sunlight.