ASTM A554 Stainless Steel Square Tube 304 Stainless Steel Square Tubing is ideal for most fabrication techniques as well as indoor and outdoor applications. This non-magnetic product features a semi-smooth, dark gray finish and tapered edges with accurate dimensions throughout its length.304 Stainless Steel is a high strength material with excellent corrosion resistance, making it ideal for marine equipment, railings, medical equipment, and food industry equipment.ASTM A554 is the standard specification for welded stainless steel mechanical tubing.