I've never used or seen one in person but they've been available it seems for 35+ years.
All I noticed from the pic is it seems to violate one of the rules of loading an antenna, the capacity hat appears to be too close to the coil.
I would expect less local vertical performance than a Whiskey still type mobile antenna.
If I had one of these I'd add 12"-18" between the coil & cap hat and remove a winding or two.
Seems a bit pricey for an oddly shaped mobile antenna, even if it does have almost 1/2 the amount of magic Antron9.9 gain