Irwin Blue Stripe Bi Metal Knife Blades pack of 10IRWIN BiMetal Blue blades combine the best of two metals electrowelded together The edge of the blade is made from High Speed Steel which is much harder than standard carbon steel and hasbeen shown to last up to THREE TIMES LONGER in user trials on plasterboard drywalling roofing insulation flooring and other heavyduty materialsThe bulk of the blade is made from spring steel which can resist pressure applied from the side without snappingThe safest blade in use is generally a sharp one it takes less effort to cut and therefore greater control can be maintainedThis blade stays sharp up to 3x longer than standard blades HighSpeed Steel Edge Heat treated to greater hardness for longer life and edge sharpnessFits all standard knivesPkt Qty 10