The MT 4 FB mount is made as a support for the MT 1 mount, it's designed for the 1 1/4" x 1 1/4" receiver. This mount is designed to fold back to allow you to open the doors on your SUV or let the tailgate down on your pickup. 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.