Question: what is the difference between a letter and a parcel?
Answer: Large Letters have a maximum length of 353mm x 250mm with a depth of no more than 25mm. And weigh no more than 750g. A parcel is anything bigger than this, but has a maximum length of 610mm x 460mm x 460mm. And weigh no more than 20kg For Royal Mail 24®, and 2kg For Royal Mail 48®.