Not recommended. They are universally maligned by guys around here as "suicide shackles". 4x4 publications don't think much of 'em, either. I looked into them a few years ago and decided they were detrimental to my rig.

A gas tank skid plate is a better use of cash, IMO.

http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=73;t=001590;p=4