This is a departure from the run-of-the-mill suction cup attachments in so far as this little gadget has a rotary mechanism that you simply twist to get it to stick to the windscreen as opposed to a lever, and this makes the whole thing a lot more compact.
The method of holding the phone is by way of spring loaded arms that grip the phone on either side (actually, only one arm is spring loaded, the other is fixed). The grips hinge back and forth whilst being able to pivot around the circular base thereby allowing complete adjustment of the phone's position which is held there by mere friction - there are no knobs to tighten in order to lock it into place.
If you pop your phone in and leave it there, it remains in position without any trouble. However, if like me you like to use a sat-Nav app on the phone and power it from an in-car adapter, any tension from the charger lead tugs away at the base of the phone and begins to pull it forward.
So my verdict would be this is OK if you just need something to hold a phone on the windscreen, but if you need to use it in conjunction with a charger make sure it isn't one of those curly lead types that need to be stretched a little in order to reach the phone.