The ORIGINAL SHEar & heLIX and spiral cutter non-grind design. Woodworkers know that a shear cut is far better than a straight cut. You also know that a stagger cut is much better than just a single straight knife and is a lot easier on your dust collection system. If you just happen to plane a nail or staple, it is not necessary to replace expensive knives the full length of your planer head. Replace 2 or 3 small inexpensive knives and you are ready to go. The SHELEX is extremely quiet compared to other blades.