0345 200 2828

By Royal Appointment to HM The Queen. BSI Certified FM31516

100% Recycled Mailing Bag
150mm wide x 229mm length, 55 micron thickness. (Large Letter).
From £10.66 per 200

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M4 Expandable Cardboard Envelope

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MCEM4 M4 Expandable Cardboard Envelope

324mm wide x 382mm long (flat) / 250mm wide x 312mm long x 70mm deep (expanded)

M4 size Amazon-style cardboard envelope with expandable side gussets that can be turned into a cardboard box. Also known as a postal M-folder, book box or capacity mailer. 100% recyclable. Boxed in 25's.

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Size diagrams Popup & zoom

Order Quantity	No. in pack	Price per pack	Price per pack	Price per 1000
		(Inc. VAT)	(Ex. VAT)	(Ex. VAT)
25+	25	£23.45	£19.54	-
125+	25	£19.31	£16.09	-
250+	25	£15.74	£13.11	-
500+	25	£12.30	£10.25	-

M4 expandable cardboard envelope - features

Send flat as an envelope (324mm x 382mm) or expand out into box-form (250mm x 312mm x 70mm).
Integral peel & seal adhesive strip means easy opening.
Rip-strip allows for quick and simple customer opening.
Lightweight postage solution, yet provides robust protection for mail contents.
E-commerce retailers will love this flexible and innovative packaging solution.
Adjustable width, length and depth (depth decreases as width/length increases).
Ideal for sending a range of products via mail or courier.
Used regularly by Amazon - also known as an M-folder, book box or capacity mailer.
Parcels will meet Royal Mail's 'Large letter' or 'Small parcel' size brackets - see details below.
Corrugated cardboard - board grade 125K/T.
100% recyclable - suitable for regular kerbside recycling collections.

M4 expandable mailer - dimensions when flat

Width: 324mm (13")
Length: 382mm (15")

M4 expandable mailer - dimensions when expanded

Width: 250mm (10")
Length: 312mm (12")
Depth (gusset): 70mm (3")

Royal Mail sizing - M4 expandable mailer

On Royal Mail's Pricing in Proportion scale, this package fits the 'Large letter' category (when depth is no more than 25mm) or the 'Small parcel' category (when depth is more than 25mm).