B3 general purpose fill & fix expanding foam is a high quality polyurethane based expanding foam designed to give excellent thermal and acoustic characteristics. Expands up to 30 times its original volume, quick to dry and can be sawn, sanded and painted once fully cured. Ideal for filling and insulating irregular or awkward gaps where the foam can expand and fill the cavity to prevent heat loss and deaden sound. Can also be used as a temporary fix prior to mechanical anchors being installed to windows and door frames.