I bought this product specifically to keep the birds from nesting in my Leaf Guard Gutters. If you're familiar with Leaf Guard, you know that there is a hood on the gutter that keeps leaves and debris out, while rain clings to the cover and through the scientific principle known as liquid adhesion. This allows rainwater to travel around the hood and into the gutter, while deflecting leaves and other debris to never clog. So what you're left with is a gutter that has a slot about 1 - 2" wide. On the west side of my house there is a gutter just below my upstairs master bedroom that is shaded in the summer and gets very little rain water in it. Birds had made a habit of nesting in the gutter and their chatter would drive me nuts in the mornings. These gutter brushes were very easy to install and did the trick. NO MORE BIRDS!!! I haven't had any issues with the brushes. They were easy to push into the slot on the gutter and once inside the bristles expanded out to take up the space so birds can't enter. I haven't noticed any issues with the gutter or water flow since I installed these earlier in the year. If you're looking for a solution to a bird nesting problem like mine, give these a try.