3" inches Replacement Reflector Crystal for Safety Sensors Photo Eyes Compatible with Seco-larm EMX Omron Accommodate most popular sensor brands Compatible with EMX NIR and NIR50, Aleko LM104 and LM104A, Omron E3K 3" inches circular wide (Please allow some measurement of about 1/8" for corrections) 1/4" inches thick Not all compatible brand and models are listed