This Firepower 1440-0220 ER70S-6 Mild Steel Solid MIG Welding Wire has a 0.035-inch diameter. It is premium AWS Class ER70S-6 used for general purpose MIG welding and is designed to be used on mild steel. It is best used with clean or prepared welding surfaces and requires a shielding gas. DC reverse polarity. 2-pound spool.