Fish Magnet,
The R-399ID-IHN is Airmar's model number of an in-hull transducer. The R-309 is the thru-hull version of that same transducer. Both transducers have the same power and frequency capabilities.
Thats what I thought. They must have made a mistake in the electronics quote-I definitely have a thru hull transducer so it must be the R309. It works very well- I can run at 40 mph and see the botton in 3000 t0 4000 ft. I am curious to see what the enhancements are with the CHIRP technology. It must be incredible