When you buy Challenge SCM dies and accessories for your SCM Manual or SCM Hydraulic corner rounders online, you not only reduce any strain on your machine that may be caused from using a dull blade, you also guarantee a perfectly clean rounded corner for your paper and plastic materials. When combined with the SCM Manual corner rounder, these knives and dies can cut cleanly through a 2" thick stack of material. When combined with the SCM Hydraulic corner cutter,however, they can round edges of stacks up to an unheard of 4" thick. Made of premium materials for a long life, these SCM dies come in a large variety of sizes including 1/8", 1/4", 3/8", 1/2", 5/8", straight and a 45° configurations. Because these knives and dies are not sold in a set, you only need to buy what you need to replace: so if your die is fine but your knife needs replacing, you only need to purchase a new knife; this way you are not spending money on unnecessary consumables before they are needed. However, both a die and a knife are required for the machine to work properly, so be sure that you have a full set before running your machine.