Just want to throw in my $0.02 if someone's on the fence. I own 2 of these for engineering work (0.5 and 0.35, both silver) and they are incredible. The main difference between the 600 and the 800 is that the 800 has a retractable tip (if you tend to snag the tip in your pocket) and I think someone mentioned it can lock the lead so you avoid more coming out if you hit the button. Unless you need those, go for the 600. The 600's fixed lead pipe (as opposed to the 800's retractable one) means the 600 is actually a bit more solid than the 800 and gives you more precision. If you want a solid, well-weighted pencil, it literally does not get any better than this.