If you search for "artec" on ebay you can find the same things even cheaper (unless GFS has Artec customize them in some way, but the pictures look identical).
I have a couple to play with, but I haven't installed them yet (Unfortunately I won't get to these projects for a while
). When I jumpered them up outside of the guitar to test, they sounded fine in a "does something interesting" sort of way without any obvious disqualifiers. Whether they will actually get much use or not once installed remains to be seen...