Our M4 Expandable Cardboard Mailers measure 312 x 250 x 70mm and mirror the cardboard mailers commonly delivered by Amazon, simply with a plain outer print design. These versatile corrugated cardboard envelopes have been manufactured using eco-friendly materials, offering expandable space to accommodate various items such as books and electronics while ensuring their safe transit. Easy to use and environmentally conscious, these cardboard envelopes are the ideal choice for individuals and businesses committed to reducing their environmental impact without compromising on quality or functionality.