COLORBOND® Coolmax® steel is pre-painted steel designed to provide and maintain a high solar reflectance. The painting complies with AS/NZS 2728, and the steel base is an aluminium/zinc/magnesium alloy coated steel that complies with AS/NZS 1397. Minimum yield strength is G550 (550 MPa). Minimum coating mass is AM100 (100g/m2). The base metal thickness (BMT) is 0.42mm or 0.48mm, depending on the product.