They consist of a single plastic bar with a rubber blade, no metal parts, and none of those complicated mechanisms to exert pressure on the screen. We get them in a local Chinese shop for five euros a pop. and think they are the biggest improvement in wiper technology in years.
Over time the wiper arms get twisted and need adjusting, the juddering is caused by the wiper blade not flipping over correctly, twisting the wiper arm carefully should cure it.