PiP large letter boxes

PiP large letter boxes are slim postal boxes designed to stay within the Royal Mail large letter size and weight limits, so flat items can be posted at the large letter rate rather than as a parcel. Custom Postal Boxes, a project of Vertex Packaging based in Wolverhampton, makes PiP large letter boxes in house with custom print, low minimum order quantities and free UK delivery.

How PiP large letter boxes keep postage in the lower band

PiP means Pricing in Proportion, the Royal Mail system that sets postage by the size and weight of an item as well as the service chosen. For a large letter, the packed item must be no more than 353mm long, 250mm wide and 25mm thick, and no heavier than 750g for standard services. A purpose made box uses that allowance carefully, with thin but rigid board protecting the contents inside the 25mm depth, instead of a padded bag that can bulge past the limit at its centre.

The 25mm depth is the measurement that matters most

Most failures happen on thickness. Tape ridges, a bulky closure, thick fill or a product that sits unevenly can all push one point of the pack over 25mm, even when the box itself is within size. Pack the item flat, spread any accessories beside rather than on top of the main product, and measure the finished pack at its thickest point. The official Royal Mail page for tracked services confirms the large letter limits, including the maximum dimensions and weight bands in current use.

Weight still counts alongside size

A box can be within every dimension and still leave the large letter band if the packed weight passes 750g. Board choice, the product and any printed inserts all count towards that total, so weigh a finished sample on kitchen scales before ordering boxes in quantity. Slim corrugated or sturdy card constructions help keep the pack light while still resisting bending.

Choosing PiP large letter boxes for your products

These boxes suit prints, documents, books, calendars, clothing accessories, cosmetics and other flat goods that need more protection than an envelope gives. A rigid box resists bending and corner damage, presents the brand better than a bag, and often fits through a letterbox so deliveries complete first time. Compare our large letter postal boxes, C4 postal boxes for A4 sized contents and letterbox postal boxes for letterbox friendly despatch.

Print and protection within a slim profile

Even a slim box has two large flat panels, which is generous branding space for a logo, a pattern and handling guidance. Inside, a thin card stiffener can add bending resistance for prints and photographs without using much of the depth allowance. Avoid loose fill that gathers in one place, keep seals flat, and if the contents are fragile at the corners, choose a box with folded corner protection built into its construction rather than adding bulky padding.

Ordering PiP large letter boxes from Custom Postal Boxes

Tell us what you post, its packed dimensions and its weight, and whether staying in the large letter band is essential on every order. Pricing depends on size, material and quantity, and ordering is quote based with free design support, so print can be planned around the slim panels. Boxes are made in house in Wolverhampton, and a packed sample check at your end confirms the finished pack before larger quantities follow.

See the full postal boxes by size range for neighbouring formats such as A5, then contact us for a quote with your item measurements. If some orders will exceed large letter size, we can quote a matching small parcel box in the same print so your range stays consistent.

FAQs about PiP large letter boxes

What does PiP mean on a large letter box?

PiP means Pricing in Proportion, the Royal Mail system that prices post by size and weight. A PiP large letter box is sized so the packed item stays within the large letter limits and is charged at that rate rather than as a parcel.

What are the Royal Mail large letter limits?

For standard services the packed item must be no more than 353mm long, 250mm wide and 25mm thick, and weigh no more than 750g. Measure and weigh the finished pack, including tape and contents, at its thickest and heaviest.

What products suit PiP large letter boxes?

Flat and light products suit them best, including prints, documents, slim books, calendars, accessories and cosmetics. The rigid box protects against bending and corner damage better than an envelope or a thin mailing bag.

Will a PiP large letter box fit through a letterbox?

A packed box within the 25mm depth limit will fit through most standard letterboxes, which helps deliveries complete when nobody is home. Letterboxes vary, so very wide items should still be checked against the opening width.

Can PiP large letter boxes be printed?

Yes. The two large flat panels carry logos, patterns and handling messages well, and inside print can add a thank you note. Free design support is included, with low minimum order quantities and free UK delivery.