The item works great. It gives you the HD quality signal.

Installed THD400 Unit attached to Clarion VX401 in a 2001 Corvette with Bose Speakers. I can definately discern a difference in the clarity and audio quality of analog FM stations. I would highly recommend this product to anyone.

I was not impressed with the unit as the digital signal was in and out a lot and didn't matter which station I was listening to even one's that are 15-20 miles away that normally come in with no issue at all, would not purchase again.

The clarion HD tuner is just OK. The sound is slightly better quality for FM. I live near two large metropolitan cities and I am just not overly impressed with it's reception over my regular antenna to receive a signal, it does not boost and It does not quite "lock on" to frequencies all that great, seems similiar to my regular radio. The additional "HD" stations do not all come in well either. It seems just when you start listening to a song on an HD station, you lose the reception completely. I have owned this for six months, and I cannot see any reason to recommend this to anyone.
Installation was a breeze, I recommend heavy duty velcro for mounting.

This thing whistles as it drops into and out of HD mode on AM stations in the SF Bay Area. If it wasn't so much of a hassle, I'd remove it. I may anyway. I certainly wish I'd have saved my money and the unpleasant listening experience.