Buzz Hollowfill is a single component polyurethane-based repair liquid for filling hollow spots and re-attaching loose parquet or boards. When injected through a small hole in the affected area, Buzz Hollowfill expands beneath the previously-bonded flooring, producing a foam, which allows a new bond to form between the substrate and the timber. Open time depending on moisture content of surroundings, but typically 30-40 minutes.