There was a thread on this sort of thing about 6 or 8 months back. I think they were among the varieties discussed. General conclusion was fine if they fit the work you do. I'm not sure that I really understand the need for the ball joint bit. Have heard that similar DIY versions with simple pivots at the bottom and a half circle pin at the top work fine. At that price its a fairly fine line between make or buy anyway.
Clive.
PS They are quite long and sprawl out rather. Especially if holding thinner workpieces. If you have a smaller machine best to mock up and check how much space you have. Probably not ideal as your one and only set. Can't see them fitting on smaller rotary tables for example.
Edited By Clive Foster on 26/02/2017 12:53:38