A4 Letter weighing up to 500g. The large envelope rate of postage applies to flat items, such as an A4 sheet of standard paper. Documents, brochures, magazines, CDs and DVDs fall into this category. To qualify for this rate of postage, items must weigh no more than 500g and meet the following size requirements: Minimum: 140mm long, 90mm wide, 0.18mm deep (with a tolerance of 2mm) Maximum: 400mm long, 300mm wide; 25mm deep