http://www.acmoc.org%2Fbb%2Fshowthread.php%3F10836-Caterpillar-Undercarriage-Wear-Gauge-Set&ei=qBeMUu67OMiX2QWwjIHgBQ&usg=AFQjCNG8mW8u5xZsBCQqsSnGZklvPn3g6w
Not sure how well this copied via phone...ok...search undercarriage specs...
http://www.acmoc.org/bb/showthread.php?15257-reversing-tracks-to-extend-life-on-a-D4/page2