Everyone else said it so I will not repeat it.
Mine are 20-years old and flying 19.5-years over 3,200 hobbs hours. I can pick up a VOR signal most of the time before I can pick up the ID signal. It is reported to me by Bob Archer (I use to live a few miles from him and purchased mine directly from him at his residence 20 some years ago.) that they have a dead spot but I am not a good enough pilot or test engineer to find it. (Note: I have an FAA Commercial Certificate, Instrument rated, fly RV Formation that include being part of most large RV Formations at AirVenture Oshkosh for the past 18-years, and now retired from a job that was Test Engineer & System Engineering.)
IMHO, IF they are installed as directed, they are the best VOR antennas that money can buy.