Stainless Steel Hex Bar is a six sided bar that are annealed and cold drawn, where the size is measured from flat side to flat side. 15-5 is a variant of the older 17-4 chromium-nickel-copper precipitation hardening stainless steel. Both alloys exhibit high strength and moderate corrosion resistance. High strength is maintained to approximately 600 degrees F. The 15-5 alloy was designed to have greater toughness than 17-4. This improved toughness is achieved by reduced delta ferrite content and control of inclusion size and shape.