After I had been looking for a door and window stopper that have "old" models, as my mother had still not found, I ordered this futuristic stopper for me. The stoppers are color very appealing. The material feels good. A small manual explains how to use the stopper - but would not have been really necessary. I have the same again 5 ordered a few tests because these stoppers (oblique or open) not only for windows but also for our patio door, balcony door and the basement windows Adjust (all have different distances from the window frame, if they are open). Even our front door, which has only a small gap to the ground, we clamp on with these stoppers, if we carry such as purchases pure.
Conclusion: They look beautiful. Beware diverse windows and doors. Very easy to handle and bring some color to the window.