The name says it all. The factory springs were pretty soft and unstable; I thought my bed had warped at some point because I just couldn't get everything straight with the hot end on the corners after making sure Had the bed was really flat I ordered it and installed it - after about 15 minutes of very careful initial calibration the bed held its position for the last month.Much cheaper and easier to set up than the BLtouch module., and scored some pretty incredible ones Results.