[Sintron] 3 pcs Mechanical Endstop Module V1.2 for 3D Printer RepRap Prusa i3 Kossel Delta etc. Mechanical switches are less complicated to implement and cheaper than optical endstops . The function of endstops are to determine the original position of the extruder hot end , so it knows where to extrude the plastic material. We not just sell them, we also provide professional after-sales service, so welcome to discuss with us, we will try to do technical support as much as we can.