If you add a glass bed on top of your Dreamer's aluminum build plate, you will need to lower the z-axis so that the nozzles don't crash into the glass. Based on salbemerson's Creator Pro shim, this thing is specifically designed for the FlashForge Dreamer and a 1/4-inch (6.35mm) piece of glass. It is a snug fit so no double-sided tape or glue is needed to hold it in place. To install, you need to remove the plastic Flashforge logo plate, which is held in place with two screws. Then place the shim on the edge of the metal lip as shown.