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Taiss/30 cm Adjustable M18 Diffuse photoelectric Switch Sensor Optical dc Three Lines NPN NC(Normally Closed) Proximity Switch 6-36VDC E3F-DS30B2: Amazon.com: Industrial & Scientific
uxcell 4mm Inductive Proximity Sensor Switch Detector NPN NO DC 5-30V 200mA 3-Wire SN04-N for 3D Printer Probe Bed Leveling,MCU Board: Amazon.com: Industrial & Scientific
Amazon.com: Taiss 2PCS M12 4mm Sensing DC 5V NPN NO(Normally Open) 3D Printer LJ12A3-4-Z/BX-5V Cylinder inductive Proximity Sensor Switch Work Voltage 5VDC Special for MCU : Industrial & Scientific