10XX steels are basic carbon steels. Basically they only consist of Iron, Carbon, Manganese, Phosphorus, & Silicon. However, there may be other elements added, especially from Aldo, so this chart is mainly for basic comparison. The main difference is the carbon content which is designated by the last 2 numbers. There are many other 10XX series steels but these are the ones mainly used by knifemakers so I didn't list them all. Just remember that if you come across some 10XX steel that it will make a knife as long as the Carbon level is 0.50 or higher.