This Garmin GTX 330 Mode S Transponder (part number 011-00455-00) is available for purchase. The item was working when removed for an avionics upgrade.  No paperwork is provided.  The serial number is 84111755.  Includes unit, mounting tray, backplate, and connector only.  

Returns accepted within 30 days - buyer pays return shipping.

Shipped USPS Ground Advantage.