Garmin stud / flange-mount version of the GA 56 low-profile antenna provides excellent reception for your panel-mount unit. TSO'd to C129 Class A-1. Comes with hardware. Antenna connection is female BNC out.
As the Garmin GA 56 is a Garmin Antenna, there is only supported information in regard to Garmin Units. There is no data on using this antenna with another manufacuters product.
No, this antenna will not work for that transponder.
Yes, this antenna can be used for a G3X system.