The sockets are thin walled, but made from Chrome Molybdenum, and are to be used in place of both impact sockets and/or chrome sockets. They're like thin-walled impacts. My SAE set goes to 1-1/2 inches and includes 1-3/16. Most chrome sockets are chrome-vanadium, and people will have differing opinions, but I prefer chromoly tools, as I think it's stronger, depending on its heat-treat and so forth. The grey tools seem to hold up to my abuse well.
They have a hole through the side for impacts, as well as divots inside the other walls in the female square for quick-release ratchets. I think they look cool too. (no, I don't work for them or anything - although I am selling a couple sets of these in the classifieds)
As you can see here, they are also stamped with Snap-On date codes as well, like my Bahco sockets (not sure what that's about, but I'm fine with it).