Good news is that I have a set of these sitting on my desk. Bad news is that I have no idea what thread they are. The head is a 13mm and the threaded portion of it is 30mm. If nobody else knows I could swing by the hardware store and figure it out.
I double checked when I was at the hardware store today. M10x1.5x30mm. Don't forget the big fat 10mm thick washers that go between the body and the carrier.