Capacity mailer envelopes are rigid board envelopes with a 70mm expanding gusset. The extra depth takes books and boxed items, and the mailer still looks flat and neat. Pack Solution supplies four sizes, M1 (219 x 155 x 70mm) to M4 (312 x 250 x 70mm), in boxes of 50 for UK booksellers, retailers and online shops.

Key features of these board mailers

• Rigid board construction: a firm board envelope, where a soft mailer would give way.
• 70mm expanding capacity: the gusset opens out for thicker items.
• Retail-ready finish: these flat cardboard mailers are sent flat and arrive looking clean.
• Four sizes, M1 to M4: they cover A5 sized items up to A4.
• Boxes of 50: simple to store and to reorder.

Capacity mailer envelopes: sizes and specifications

Dimensions are given as length x width x expanded depth.

All four sizes are rigid board capacity mailers with a 70mm expanding gusset, and each comes in a box of 50 envelopes.

Which size do I need?

• M1 (219 x 155 x 70mm): takes an A5 item (148 x 210mm), such as a paperback or a small boxed product.
• M2 (250 x 165 x 70mm): larger paperbacks and accessories.
• M3 (285 x 205 x 70mm): hardbacks and gift sets that are just under A4.
• M4 capacity mailer (312 x 250 x 70mm): takes an A4 item (210 x 297mm), so it is the one of the large gusset envelopes to choose for A4 books, folders and several books at once.

Check the thickness of your item as well, since the gusset expands up to 70mm.

Ideal for

• Rigid cardboard mailers for books and multiple books
• Cardboard mailers for boxed products
• Board mailers for gift sets
• Clothing and accessories

Bulk and trade pricing

We sell book mailers in boxes of 50, priced per box excluding VAT. The price per box falls automatically as you order more, using the tiers on this page. The minimum order is one box, and every order comes with a VAT invoice. Booksellers and trade buyers can call 0161 706 1246 or email [email protected] for larger quantities.

Delivery and collection

Orders placed by 2pm Monday to Friday are dispatched the same day from Manchester. Royal Mail Tracked 48 is free on every order with no minimum, DPD Next Day is 7.99, and click and collect from Manchester M8 8HF is free. See our delivery information.

Frequently asked questions

What is a capacity mailer?

It is a rigid board envelope with an expanding gusset. Ours open out to 70mm deep, so they hold books and boxed items that would not fit a flat envelope.

Which capacity mailer fits A4?

The M4 (312 x 250 x 70mm) is larger than A4 (210 x 297mm), so it works as A4 gusset envelopes for books and folders. The M3 is 285mm long, which is too short for A4.

How deep do capacity mailers expand?

All four sizes expand to 70mm deep, which suits them to use as gusset envelopes for books.

How many capacity mailer envelopes are in a box?

Each box holds 50, and every cardboard mailer arrives flat.

Related products

For flat items, see board back envelopes and bubble pouches, or white padded envelopes for small products. Browse all envelopes and mailers, or read common shipping materials every business needs.