3PCS SainSmart Optical Endstop Switch for 3D Printer Arduino MEGA2560 R3 Optical Endstop Switch Kit for CNC 3D Printer RepRap Makerbot Prusa Mendel RAMPS The optical endstop is a reliable endstop / switch solution for any type of 3D printers and other CNC and/ or 3D tools. 3 Pack