The cutting edge can be prepared in different ways. A sharper edge will cut very easily with lower cutting forces and a clear shearing of the material but it is more delicate. A stronger edge with some honing or rounding will last longer under load but it comes with slightly higher cutting forces so there's always a balance to be had. Sharper edges tend to suit finishing better and stronger edges suit heavier cuts and the important point is this, you don't pick the edge prep separately. It comes packaged with the chip breaker.