For composite and upvc doors we would recommend using our door letterbox which is supplied as a full kit and contains a tunnel and brushes to reduce drafts and insulate the door. The sleeve inside the letterbox also protects the door from moisture and masks the aperture cutting.Designed to match our other aged bronze front door furniture to create a feature entrance door.Maximum door thickness: 72mm.Minimum door thickness: 42mm.Supplied with matching SS bolt through fixings.Our Aged Bronze products are manufactured from solid bronze containing a minimum of 85% copper. Due to the process used to age the metal, this finish is very dark and has a rich, matt appearance. During the final stages of manufacturing, we apply a durable, matt lacquer to this finish which helps preserve its distinctive tones.Overall Size: 315mm x 92mmOpening Size: 249mm x 41mmFixing Centres: 283mm.