Post & ship
Royal Mail Large Letter boxes
Royal Mail Large Letter boxes are cut to sit within the Large Letter size limit, so small, flat items post at the cheaper Large Letter rate instead of as a parcel. They're the go-to for ecommerce sellers posting jewellery, cards, prints, cosmetics and slim goods — the rigid alternative to a mailing bag.
The catch is depth: anything over the thickness limit tips into small-parcel pricing. Our postal box range is sized to help you stay in band, and for the full band definitions see our Large Letter and PiP glossary entries. For volume or branded boxes, request a bulk quote.
Shop the range
Large Letter limits at a glance
- Maximum size 353 × 250 × 25mm
- Maximum weight 750g
- Over 25mm thick posts as a small parcel
- Right-sizing the box is what keeps postage in band
What fits a Large Letter box
As a rule of thumb, if it's flat and light it's a Large Letter candidate; if it's bulky or over 25mm packed, plan for a small parcel instead.
- Jewellery, cards and prints — easily within the band
- Cosmetics, slim accessories and enamel pins
- Thin apparel (a single tee) — check the packed depth
- Subscription items — design the whole pack to the 25mm limit
Popular in this range
PiP Large Letter Postal Box — A5
Royal Mail Large Letter box, folds flat, 25mm deep.
Single-Wall Mailer Box — Medium
Die-cut ecommerce mailer, easy fold, self-lock base.
Custom Printed Mailer Box
Branded mailer boxes printed to your artwork.
Grey Mailing Bags — Medium
Co-extruded grey poly mailer with self-seal strip.
Related buyer guides
Before you order, check
- The internal size fits your product with room for protection
- The pack quantity matches how fast you get through them
- Postage banding — will it post as a Large Letter or a parcel?
- Whether you need a stronger grade for weight or transit
- If a recyclable or plastic-free option suits your customers
Stocked, or sourced to order
We hold the fast-moving lines and source the rest through our UK supplier network — so you get one honest point of contact whether an item is on the shelf or made to order. We don't claim stock or delivery speed we can't meet.
Stocked lines
Core products we hold and despatch in listed pack sizes. Buy online at trade pricing.
Supplier network
Custom sizes, printed and specialist lines sourced to order. Priced per order, with a lead time confirmed up front.
New lines
Products being added to the range. Leave your email and we'll tell you the moment they land.
Common buyer questions
What packaging do I need for ecommerce orders?
A box or mailing bag sized to the product, void fill or bubble wrap so nothing moves, plus tape and a courier label. Right-sizing keeps postage and damage down.
Which boxes fit Royal Mail Large Letter?
Boxes within 353 × 250 × 25mm post as a Large Letter. Our PiP postal boxes are cut to sit inside those limits so you pay the cheaper rate.
Poly or paper mailing bags — which should I use?
Poly mailers are waterproof, lightest and cheapest; paper mailers are kerbside recyclable with a premium feel but less water resistance.
What tape is best for heavy cartons?
Use a stronger vinyl or solvent polypropylene tape for heavy or double-wall cartons, or gummed paper tape for a tamper-evident, recyclable seal.
Frequently asked questions
What size is a Royal Mail Large Letter?
Are these boxes the same as PiP boxes?
What happens if my item is over 25mm?
Related searches
Buying in volume? Get trade pricing.
Tell us what you need — sizes, quantities and how often. We'll send pricing and lead time, and source anything we don't stock through our supplier network.
