Sorry for the delay, work work work. The steel is CPM-M4. It's supposed to be like the super version of D2, easier to sharpen but better edge retention, slightly better corrosion resistance (though it can still rust). That's just the hearsay, I haven't had it long enough to validate. THOUGH, I did purposefully leave it in my bathroom while I took a long hot shower to see if the steam corroded it. Didn't wipe it after and just put it in my pocket, it was really steamy in there. Checked it at the end of the day and no spots or anything along edge.
It is pretty big, but is carries REALLY well for it's size. If you're in the market for a tactical folder with great features I'd say check it out. I don't know if you can see from my pics but it has a carbide glass breaker on the pommel, kind of neat. Been my EDC since I got it.