Narco transponder AT 155 that did not pass certification due to receiver sensitivity being slightly outside the margins allowed by the FAA. Does not include tray or connector. The AT 155 is like the AT150 in many respects (and is a slide-in replacement for it and the 50A) but it is based on newer technology and is lighter at only 1.5 pounds. Good cosmetics. As is, for parts or repair, no returns or refunds.