This compensator is made to fit a 3mm glass bed so that the bed does not need to be re-levelled upon removing and adding the glass bed. This compensator fits around the back bars of the printer so that when the Z axis is homed, it provides a 3mm space between the end stopper and the bed. To make sure it does not break your glass on first install, remove the glass bed and install the compensator. Home the Z axis and the glass bed should slide in between the nozzle and bed nicely. Should it not, then only minor adjustments should be needed. Iv used mine for 2 months now, with many hours of printing and has not failed me yet. Let me know how it works with your printer and if there are any improvements you would like. Enjoy!