Well at least it's secc steel but 0.5mm that's going to be like sticking you hand in a bucket of razor blades.
And the 343, width is only 180mm with just 146mm cooler clearance and an 80 or 92mm rear fan.
That's so pants compared to the old 340 case.
All told coolermaster still seem to be moving backwards in their cheap cases.
Umm CAT look at those thickness & weight numbers again, you might notice a correlation
a 0.6mm steel case is very noticeable lighter than a 0.8mm steel case even with a full pc build inside.
It's also noticeable weaker, I'll happly stand on the old 0.8mm chieftec cases we've got at work, even the slightly later 0.7mm ones they are solid, I'd not dare to stand on the new 0.6mm cases (or should that be works of origami) I can make the top panel flex by just pushing on it with my hand.
Granted I can carry the new pc's to the other side of the building with only one arm, need both arms to move the old ones any distance.