GutterBrush is a simple twisted-in-wire brush similar to a large heavy-duty bottle brush. It's constructed from a galvanized steel core and double UV-protected, durable polypropylene bristles. When installed, stiff GutterBrush bristles fill the gutter, blocking leaves and debris from entering. The entire gutter remains open, allowing water to flow freely through the brush and drain path. Be sure to measure your gutter opening from the back of the gutter to the front lip to choose the proper GutterBrush.