With over 1, 500 sizes available Boxes Fast offers a large variety of packing boxes to choose from. Boxes Fast BF40604PCMC adjustable corrugated cardboard mirror boxes 40 x 60 x 3 1/2 inch (L x W x H) come with four separate box pieces that create one “custom fit” moving box. Carton panels feature fragile, handle with care and do not lay flat messages, making them ideal to ship mirrors, pictures, or other glass items. The single wall C-Flute corrugated fiberboard provides structural strength and crush resistance; making these cartons a durable choice for all packaging needs. Boxes are shipped flat to save on storage space and reduce freight cost. Corrugated cartons come in the standard Kraft color, and are made of recyclable cardboard. Listed dimensions refer to inside usable carton space.