Kirby standard steel panels are 0.5 mm or 0.6 mm thick and have a minimum yield strength of 345 MPa. Steel panels are hot dipped and galvanized with zinc or zinc-aluminium coating. Galvanized materials conform to G90 for 275 grams per square metre according to ASTM A653. Zinc-Aluminium coated materials conform to AZ150 according to ASTM A792.