its basically a unit that gives you dual options for the trasnfer case (duel case). You can have your standard low range, ie 1.90 & then you can select the marlin range of 4.70 (or whatever is in there). It means having 2 selectors & a bit of mucking around with linkages etc to get it all working. Gives you heps more options that just than a straight 3.15 gear, but its getting marlin to be interested is the problem & also if there is much interest.

I also emailed Matt but nothing back yet. Could of even gone out of business with the GFC who knows (his website is down as well)