The cheap carbide tire studs I purchased from Amazon came in yesterday's mail. They are 12mm long and the hex head is only 4mm. Pretty small but they are the shortest ones that they had. The GripStuds that I used last year are 12.5mm long but 9mm in diameter. The GripStuds are the ones listed in the Aerostitch catalog and they worked well. Not a single one came out on their own.
Here is what they look like when they are installed in the front wheel. I guess I am a little concerned that they will push further into the tire as the tire wears. As it is, 12mm is right at the limit of the tread depth and they are so small that they are fairly difficult to install with an electric drill. I don't have a 4mm driver bit and the 4mm ¼" socket is almost too deep. Maybe if I can find a small magnet to install inside of the socket to take up some of the depth.
The only benefit to the cheap studs is that they are cheap. 35¢ each is easier to swallow than $1.08 each for the GripStuds. In this photo you can see the real advantage of the GripStuds.