Hi @hae_newkirk! This hardware is rated for up to 300 pounds per pair of hangers, meaning you could mount more than one 300 pound door on the same track because each door will have its own pair of hangers. There is no maximum thickness; we just recommend having at least a quarter-inch of clearance between the door and the wall. To accomplish this with very thick doors, the hangers do not have to be installed in the center of the door. Here is a link to our installation manual for this product; see page 6 for additional information. And please feel free to message us if you have any other questions! -Rejina