The MT 3 OS mount is made as a support for the MT 1 mount, it's designed for the 2" x 2" receiver. This mount is  also offset in order for you to get an unobstructed view of that custom license plate. Also, on split door SUVs it lets you open the right door. This mount is also 304 stainless steel. The mount comes with an installed anti-rattle kit.  Designed for use with the M100, M200, M300 & M400.   Not designed for use with the M40, M75, LT-HP, LT-II or BTA