Hardox® 550 At 550 HBW and with a toughness close to Hardox® 500 Hardox® 550, with a nominal hardness of 550 HBW and toughness close to Hardox® 500, increases wear life but not at the expense of crack integrity. Mechanical Properties Thickness(mm) Hardness 8.0 - 65.0 525 - 575