I have a Rat II they are AUS-8 steel.I've carried and used it every day for a couple years.They are a very solid well build knife.AUS-8 is no super steel but hold a decent edge and doesn't take much to touch it up.For $25 they are a very good knife.They make the Rat-II in D-2 I lost my knife for a couple days and ordered a D-2 one but haven't used it.If they make the Rat-II in it I would think the Rat-I would come in it too.
The Japanese-made AUS 8 steel is often considered an upper-range steel, comparable if not better than steels such as 440C, CM-154, and D2 steels. Given a proper heat treatment and hardened to the right level, which is usually around 58 to 59 HRC, it will perform satisfyingly and meet the standards of a true quality stainless steel. A well-rounded composition allows for this steel grade to reach high levels of hardness, toughness, wear (the sideways shifting of the metal from its original position) and corrosion (the gradual destruction of metals) resistance, as well as edge retention (the ability to retain its sharp edge).
The only AUS-8 knife I have is the Rat-II.I know in the knife I have it doesn't hold a edge nearly as long as knives in the steels birddog listed.I still like it holds an edge long enough for what I use it for and very easy to get scary sharp.But if I needed to use a knife long term and not be able to touch it up I'd carry something else.