I love this window hook.  Simply wash your window and soak the suction cups in warm water for 2 minutes and then attach to your window.  I tried it out with a light weight hummingbird feeder and it stayed stuck to my window just fine.  I was limited as to where I could hang it since the majority of my windows have full screens but it worked fine on my full glass patio door.  I liked that you can hang it with the hook up or the hook down.  Since it will hold up to 3 lbs I may use around the holidays to hold my wreath to my front door.  I highly recommend it, it works great.