A must have for 3D Printer Hot Bed/ Platform, bottom connect, serve to replace on your heating bed original springs. They're much stiffer than the stock springs and allow to really crank up the print speeds, so parts finish sooner with no loss in quality Special design for Ender 3 S1 Pro/ Ender 5 plus/ Ender 5 Pro/ Neptune3/ Ant A8 / Wan hao D9 / Megai3 Pro/ SW X1/ Monoprce Make Select or other heated bed that has a auto bed leveling sensor