The new Royal Mail Pricing in Proportion (Pip) System requires that both the weight as well as the size of the item taken into account.
The design of the Royal Mail Approved PiP Ruler enables both the size and thickness of the envelope to be simply and accurately measured.
Salter PiP Ruler covers the three sizes for ordinary mail:
Letters > small and medium up to half the size of A4
Large Letters>envelopes up to A4 size-Packets