If you are considering ADS-B in a small panel, consider the Trig TT22.
Soap Box Moment;
Most small panels, like Cub panels, were never intended for 'square' avionics (anything with a tray). That means when one of these are installed, you'll need to make the panel stiffer/stronger and brace the tail end of the tray. And the tray location is limited due to the tray contacting the tubing forward of the panel. Transponders like the Trig are mounted like a small instrument, with four screws and no tray. To make it into an ADS-B out system, just tie a WAAS GPS signal in on a data line. Smaller, lighter, less space.
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