13- Inch HSS Planer Knives for Ridgid 27263 Planer, Ridgid R4331, R4330 Planer, Replaces AC20502 - Set of 3 13-inch Replacement Planer Knives for Ridgid R4331, R4330 Planer Made of High Speed Steel for longer cutting life Double-edged "reversable" high-speed steel construction Blade material: M2/SKH51/W6Mo5Cr4V2 Hardness: HRC 65-68° Set of 3, Plastic case packaging 13-inch Replacement Planer Knives for Ridgid R4331, R4330 Planer Made of High Speed Steel for longer cutting life Double-edged "reversable" high-speed steel construction Set of 3, Plastic case packaging