The BES 516-209-S21-E is an inductive proximity sensor with dimensions of 12 x 70 mm, featuring a connector interface and normally open (NO) configuration. It operates at 20/250 VAC/DC with a current range of 5/130 mA, offering a sensing distance of 4 mm in non-flush mounting. This model has been discontinued by the manufacturer and is replaced by BES M12MH-UST40B-S21G (BES05ZL).