LYNN ATT-SU-10 (Millennium part 521005) delivers a fixed 10 dB pad in a male-to-female SC/UPC singlemode body, sized for links so short that transmit power would otherwise overload the far-end receiver. Ten decibels is the common value when bench-testing high-power transmitters or looping a metro span back on itself, letting engineers simulate distance without spooling extra fiber. The ultra physical contact ferrule keeps insertion loss and reflectance stable across repeated matings. RoHS compliant and inline-installed, it belongs in every test kit alongside your OTDR, light source and optical power meter.