I removed a Narco AT 150 TSO transponder from my Mooney M20-C and replaced it with a Garmin 345 to meet the ADS-B out requirement. As such I have an "as removed" Narco transponder for sale. It worked perfectly for the 5 years I had the Mooney. My Mooney is a 14 volt system and this one appears to work with either 14 or 28 volt. I looked on ebay and they are selling for anywhere from $100-$750. If anyone wants it for $100 message me. I am going to put the same message on the Twincessna.org webpage as well. If no one wants it I will put in on ebay in a week or so. Also I will have Cessna 340 airspeed indicator, DG, altimeter in the near future as there will be more upgrades. If you need any of there please let me know as well.