Put this on my Fat Bike/Snow Bike because I don't want to be the source of a good laugh when my bike throws me on the ice in front of 12 guys. They are amazing! Each bag had an outlet to power it. I used my grinding wheel to shave about 3/16 of the socket surface. If you drive them with an outlet, the outlet will bite into the tire. You either drive it halfway in with a socket, then tighten it with pliers, or sand down the front of the socket. The spikes themselves are the perfect size (9mm) and fit snugly in the tire.