Review on HSS Jointer Replacement Blades for 20 Inch Planer Knives - Grizzly, Jet, Powermatic, Delta, Dewalt, Shop Fox, Woodstock, 4pcs Set by Matthew Kocur

Knives are sharp as expected. Although I've only been on a planer with these knives for a few hours, I would say they retain their sharpness after planing some very hard (white oak, ash) boards. There are probably tougher knives out there, they cost significantly more, so I'd say these are good knives for the money, at least for the DIY enthusiast. For professional (intensive) users I can offer more expensive knives so that they do not have to be changed as often.