We carry a set of 4 of these:
http://www.tirechain.com/square_alloy_cross_chain.htm
With the 37" MTs and lockers we have had no need for them until this winter. We did finally get to use them however, when taking a "short-cut"
in late December.
The snow was about 3' deep, it was compacting under the tires till the tops of the axles were about even with the top of the snow (so pushing a bit). Down-hill was ok, but after deciding prudence dictated turning back, we required the chains to get back uphill.
They went on easily enough, tightened with cams and bungies. As straight ladder chains, they did not provide any lateral stability (we were on the side of a hill, and the side slipping required unlocking the lockers at times). But they helped tremendously with the forward going.
No pics from where we turned around (other things on the mind), but about 1/2 mile later where the snowpack was much thinner:
Anyway, they were useless (unused) for 2 years, but oh-so-very valuable when finally needed.
-Erik