Product Name : Proximity Switch Sensor;Model : SN04-N;Type : DC 3-wire NPN No;Theory : Inductance Sensor Output : Switching Transducer;Sensing Distance : 4mm;Working Voltage : 10-30V DC Response Frequency : 500Hz max;Indicator : Red LED;Size : 18 x18 x 36mm/0.7 inch x 0.7 inch x 1.4 inch (W*H*L) Cable Length : 135cm/53 inch ;Hole Size : 0.9 x 0.4cm/0.35 inch x 0.2 inch (L*W);Extenal Material : metal Net Weight : 48g;Color : Black, Green; Over-current and short circuit protection, with LED indicate, easily identifiable. The Proximity Sensor Switch is used for testing parts such as size and speed can also be used in frequency counters, frequency pulse generator, liquid level control and processing procedures for the automatic convergence. Package Content : 2 x Proximity Sensor Switch, 8 x Screws Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.