Letter/postcard:

• No larger than C5 in size (i.e. half the size of an A4 sheet)
• Also known as POP (Post Office Preferred)
• Dimensions -
• min 140mm length x 90mm height x 0.18mm depth;
• max 235mm length x 162mm height x 5mm depth.

Large Envelope:

• Items up to C4 in size (i.e. the size of an envelope containing flat A4 sheets).
• Also knows as a "flat" item
• Dimensions -
• min 140mm (L) x 90mm (H) x 0.18mm (D);
• max 400mm (L) x 300mm (H) x 25 mm (D).

Packet:

• Caters for three dimensional items like boxes, tubes and envelopes which exceed the limits of a Large Envelope.
• Dimensions: Minimum dimensions are 100mm (L) x 70mm (H) x 25mm (D)
• The maximum dimensions for a package is a combined length, height and depth of 900 mm (no dimension exceeding 600 mm)
• In tube form the maximum dimensions (the length plus twice the diameter) must not be greater than 1,040mm, with no dimension exceeding 900mm.