18mm was missing but I knew that when I bought them, . The blank socket is an extra 16mm so no harm done. Happen to have the missing 18mm, so I'm happy with the set. Sockets are the usual Proto quality and I have no complaints at all. Only mentioned it because I had never seen a blank name brand socket, am definitely more amused than anything else, even if it wasnt an extra it wouldn't bother me. Still perfectly functional and doesn't take a brain surgeon to remember the 16mm is the unmarked one. Even though I suffer from the common OCD most here on GJ do too, I limit it to having at least one of everything ( 6 point, 12 point, shallow, semi deep, deep, swivel, impact, etc. ) . been swinging wrenches for 40+ years and have still yet to look inside a socket, or ***** about a scratch here or a nick there, and yes 90% of my tools are truck brands or top tier American made, but understand that they are tools and exist only to get the job done and make me money . As long as they do that I have no *****