Ultra-slim Photoelectric Sensor EX-10 (Panasonic)

    Smallest body, just 3.5 mm 0.138 in thick

    It can be mounted in a very small space as its size is just
    W10 x H14.5 x D3.5 mm
    W0.394 x H0.571 x D0.138 in (thru-beam, front sensing type).