Custom Bubble Mailers, Kraft Options and the Size Numbers Explained
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Sizes that fit the first time, the kraft versus poly trade-off, and a branded parcel you can afford at low volume.
A bubble mailer is a padded envelope sized by number, from #000 at 4 by 8 inches of usable space up to #7 at 14.25 by 20, and that number describes the inside rather than the outer envelope. Kraft has a brown paper outer that takes tape well and absorbs water, poly has a plastic outer that is waterproof and lighter, and neither is curbside recyclable because both are bonded to a polyethylene bubble film. Printing directly on stock mailers runs in the thousands per size, so a printed label and printed tape are the low volume way to brand one. Our guide to kraft bubble mailers, the cheapest real estate your brand owns covers that approach, and tapes printing lists the tape that seals them.
Quick answer
Size by the inside, choose the outer by the weather
Pick the number by usable inside space plus half an inch of clearance, then pick the material by where the parcel ends up. A doorstep in the rain calls for poly. An office mailroom or an unboxing that should feel natural suits kraft, which also holds printed tape properly.
What a Bubble Mailer Does Well, and Where It Quietly Fails
A bubble mailer earns its place on light, flat, non-fragile goods: a folded tee, a print in a sleeve, a paperback, a phone case, a set of samples. It weighs a fraction of a box, it takes almost no storage space flat, and because it conforms to the contents it usually costs less to ship than the smallest box that would hold the same item.
The failure mode is crushing. The bubble layer inside a standard mailer is about an eighth of an inch of air film, sometimes three sixteenths on heavier grades. That is enough to absorb abrasion in a sorting machine and a short drop onto a concrete floor. It is not enough to resist a point load, such as a heavy tote set down on your parcel in the back of a van. Anything with glass, a screen, a ceramic edge, or a hinge should be in corrugated.
There is a rate rule worth knowing before you standardize on mailers. USPS treats a mailpiece as a flat only if it stays under three quarters of an inch thick, fits inside 12 by 15 inches, and is uniformly thick and bendable across its whole surface. A mailer holding a flat item passes. A mailer holding a lumpy item fails and gets rated as a package, which is the moment the cost advantage over a small box mostly disappears. Our mailer box versus shipping box guide works through that comparison in detail, and shipping boxes cover the jobs where padding is not the answer.
Kraft vs Poly Bubble Mailers Side by Side
The two mailers share the same bubble lining and the same numbering, so a 4 by 8 inch mailer is a #000 in either material. The outer layer is where they part ways.
| Test | Kraft bubble | Poly bubble | Verdict |
|---|---|---|---|
| Weight | Heavier than poly at the same size. | The lightest padded mailer. | Poly, when an order sits near a postage ounce boundary. |
| Water | Absorbs and softens, and the label can go with it. | Waterproof at the material level. | Poly for anything left on a doorstep. |
| Tear strength | Paper scuffs and tears once it is wet. | Film stretches before it splits. | Poly on long or rough routes. |
| How the print looks | Matte brown; printed tape grips it and labels sit flat. | Slick; tape adhesive struggles on it. | Kraft when the tape carries the brand. |
| Recycling | Not curbside, paper is bonded to film. | Store film drop-off, not curbside. | Neither; choose paper padded for a curbside outer. |
| Best use | Dry routes and an unboxing that should feel natural. | Apparel, soft goods and any parcel that may get rained on. | Poly by default, kraft for the look. |
Postage follows weight and thickness, not the material name, so check the current USPS rate tables for your packed weight.
Kraft, Poly, or Paper Padded, and the Honest Recycling Answer
Three materials cover almost every padded mailer on the market, and they behave differently enough that picking on looks alone costs money later.
| Type | Outer material | Water | Weight | Recycling reality |
|---|---|---|---|---|
| Kraft bubble | Brown paper laminated to a polyethylene bubble film. | Absorbs and softens, label ink can run. | Heaviest of the three at the same size. | Rejected by paper streams and by film streams, because the two layers are bonded. |
| Poly bubble | Polyethylene film outer, same bubble lining. | Waterproof at the material level. | Lightest of the three. | Recyclable at store film drop-off points, not curbside. |
| Paper padded | Kraft outer with a honeycomb or macerated paper cushion, no plastic. | Absorbs, same as kraft bubble. | Similar to kraft bubble, sometimes heavier. | Goes into the paper stream as one material. The only genuinely curbside option. |
Read the last column twice, because brown packaging is often sold as the green choice and a kraft bubble mailer is not one. If a recyclable outer is the actual requirement, the honeycomb paper padded mailer is the product that delivers it, and it costs more per unit for exactly that reason.
Weight decides the rest. Poly wins on rain and on cost per shipment, kraft on how it feels in a customer's hands. If you settle on poly, Custom Poly Mailer Ideas That Brand Every Shipment shows ways to brand the slick surface. For the wider material comparison, the paper stocks guide covers how kraft behaves under ink, and the eco friendly printing collection lists the packaging we run on recycled and uncoated board.
Standard Bubble Mailer Sizes and How the Numbering Works
Padded mailers are sold by number rather than by dimension, and the numbers run from #000 up to #7. Almost every brand prints the usable inside area on the pack, and the envelope itself is roughly an inch longer to allow for the flap and the seal strip. Match the piece to the inside number, never to the outside of the envelope.
| Number | Usable inside | Typical contents |
|---|---|---|
| #000 | 4 x 8 in | Jewelry, keys, USB drives, sample cards. |
| #00 | 5 x 10 in | Phone cases, cosmetics, small parts. |
| #0 | 6 x 10 in | Trade paperbacks, single folded garment. |
| #1 | 7.25 x 12 in | Hardcovers, folded tees, A5 print runs. |
| #2 | 8.5 x 12 in | Letter documents, tablets, catalogues. |
| #3 | 8.5 x 14.5 in | Legal documents, textbooks, larger prints. |
| #4 | 9.5 x 14.5 in | Two or three garments, boxed accessories. |
| #5 | 10.5 x 16 in | Bulk apparel, oversized books. |
| #6 | 12.5 x 19 in | Hoodies, bedding, bulky soft goods. |
| #7 | 14.25 x 20 in | The largest standard size before a box is cheaper. |
We print the pieces that go on the mailer rather than the mailer itself, and they are sized to these numbers.
| Mailer | Shipping label that fits the face | Printed tape |
|---|---|---|
| #000 and #00 | 3 x 5 in, or 4 x 6 in on a #00 | 2 in wide, across the flap |
| #0 to #2 | 4 x 6 or 5 x 7 in | 2 in wide |
| #3 to #7 | 5 x 7 in or any custom size | 2 or 3 in wide |
Shipping labels come in 13 standard sizes from 2 x 3.5 to 5 x 7 inches plus any size up to 7 x 6, on 23 stocks from uncoated paper to white vinyl and clear, ready in 3 business days or sooner. Printed tape comes 2 or 3 inches wide in 55 or 110 yard rolls on white or clear polypropylene, in one or two ink colors, by the case, ready in 20 business days. Upload the label as a PDF at its finished size with an eighth of an inch of bleed.
Before you commit to a full carton of mailers, measure a physical sample against your piece.
If you are sizing the product rather than the envelope, the box size chart by product type gives starting dimensions by category, and how to measure a box for shipping covers the length, width and depth convention carriers expect on a manifest.
Branding a Padded Mailer Without a Five Thousand Unit Minimum
A custom bubble mailer is one way to make a parcel look like it came from a real brand, and there are three, at very different price points.
Printing on the mailer itself is the expensive one. Stock mailer converters print flexographically, which means one or two spot colors rather than full color, thousands of units per size and per color, and a plate charge on each. White ink is rarely on the menu, so a pale logo on brown kraft prints as a muddy tint rather than a clean mark. Design for a single dark color or a solid knocked-out shape and it works. Send a four color logo with a gradient and it will not.
A printed shipping label is the cheap route, and it carries full color artwork at real resolution. It is the surface the customer looks at first anyway, because it is where their own name is. Printed packaging tape is the second layer, and it has a material catch worth planning around: tape adhesive grips kraft paper and struggles on the slick polyethylene surface of a poly mailer. If your branding plan is tape, buy kraft mailers. If you have already standardized on poly, put the money into the label and an insert instead.
The third route is inside. A printed card or a folded insert costs little per shipment and does the job the outside of a mailer cannot, which is to say something after the parcel is open. Packaging inserts that drive repeat sales covers what to put on one, and the custom kraft tape guide goes deeper on tape and surface pairing.
Packing Fragile Items So the Padding Actually Helps
Padding works by giving an impact somewhere to go. That only happens if the item can move a little inside the envelope, and only if the impact hits the padded face rather than a corner. Both conditions get broken by the same habit: buying the smallest mailer the item fits into.
Center the item and leave a margin. A piece pressed against the seam has bubble on one side and a glue line on the other, and the glue line is where drops land. If the item has its own retail box, tape that box shut before it goes in, because a box that pops open inside a mailer turns its own contents into the thing that punctures the lining.
Printed goods have a specific failure worth naming. A stack of business cards or postcards has four sharp corners under load, and those corners can abrade through a kraft outer during a long transit. Band the stack, slip it into a poly sleeve, or ship it in a box. The same goes for anything with a metal edge.
The cutoff: if the item would not survive an adult standing on the parcel, it needs corrugated rather than padding. For a light item that needs walls rather than crush strength, our 14pt or 18pt kraft mailer boxes do the job, and the cardstock versus corrugated comparison shows where each board stops, and the custom box printing range covers the structural end of the same shipment. There is also a short kraft mailer boxes story on that box.
Ordering Custom Mailers, and What We Actually Print
4OVER4.COM does not print bubble mailers. That is a converting operation on stock envelope blanks. What we print is everything around one, plus the printed box that replaces it when the item deserves structure.
The sensible order of spend, if you are building branded shipping from nothing, follows the cost per branded touch. Start with the label, because 25 shipping labels cost $25 and one goes on every parcel regardless of what it is packed in. Add printed packaging tape at $347.11 for a case of 36 two inch rolls once volume justifies it, since it brands stock mailers and stock boxes alike. Move to printed kraft mailer boxes or custom mailer boxes, $711.78 for 250, when the unboxing itself is part of the product, which is the point at which a padded envelope was already the wrong choice. The custom mailer boxes story shows that box in use.
Artwork goes in the same way as any packaging job: full size, with bleed, fonts outlined, and dielines respected. How to prepare files for packaging products covers the setup, and the packaging printing collection lists every structural format we run. If you sell online and want the whole parcel to match, the ecommerce printing collection groups labels, tape, boxes and inserts in one place.
Wally sizes a bubble mailer
The number on the pack is the inside, and half an inch of slack is the difference
Wally measures the item, adds half an inch each way, and only then picks the number, because a mailer stuffed tight has nowhere for the bubble to squash. Then he checks the forecast. Kraft for lobbies and offices, poly for porches in the rain. When someone asks him for a printed logo on the envelope itself, he shows them the price of a flexo run against a full color shipping label and they usually pick the label.
Print your shipping labels →
Specs and pricing
Branded shipping, sizes and starting prices
The three surfaces that make a parcel look like it came from a brand, with live configuration choices and starting prices from the 4OVER4.COM configurator. Kraft mailer boxes are 14pt or 18pt paperboard in 5 x 7 x 1.7 or 5.5 x 5.5 x 2.625 inches, from 250 in 7 business days.
Print it
Brand the parcel, not just the product
Order in the sequence the cost suggests: labels on every parcel first, a case of printed tape once volume is there, and a printed box when the item needs walls.
Explore more
Where to go next
Read the mailer box versus shipping box guide when padding stops being enough, the kraft tape guide before you pick a mailer surface, the package labeling guide for barcode clearance, and the cardstock versus corrugated guide before you choose a box.
By the numbers
Twenty five years of mailer and shipping work
Common Questions
Your bubble mailer questions, answered
What size bubble mailer do I need for a book?
Work from the usable inside dimension, then add half an inch each way. A trade paperback fits a #0 at 6 by 10 inches. A standard hardcover wants a #1 at 7.25 by 12. A textbook or an art book usually needs a #3 at 8.5 by 14.5, and at that weight the bubble is doing very little, so a corrugated book wrap or a small box protects the corners better than padding does.
Are kraft bubble mailers recyclable?
Not as sold. Paper recyclers reject the mixed material, and plastic film recyclers reject the paper. Two options actually recycle: a poly bubble mailer taken to a store film drop-off, or a honeycomb paper padded mailer with no plastic layer at all, which goes straight into the paper stream. If sustainability is the point of the purchase, the brown color is not the thing to buy for.
Can I print my logo directly onto bubble mailers?
Yes, through a converter that prints flexo, and the catch is volume, covered in the branding section above. We do not print the mailers themselves; we print the shipping label and the packaging tape that go on them.
Do bubble mailers really ship cheaper than boxes?
Usually, for two reasons. They weigh less than corrugated, and they take up less dimensional volume, which is what most carrier rate tables charge on for anything light and bulky. A chunky item changes that, because it loses the flat rate described above and rates as a package.
Kraft or poly for deliveries left outside?
Poly. Polyethylene is waterproof at the material level, so an afternoon of rain on a doorstep does nothing to it. Kraft paper absorbs, softens, and starts delaminating from the bubble layer, and the printed label on the outside goes with it. If they are suburban porches, buy poly and put the branding on the label.
How much to mail a 5x7 bubble mailer?
Postage on a 5 x 7 bubble mailer depends on its packed weight and thickness, not on the size. Under three quarters of an inch thick, bendable, and inside 12 by 15 inches, it rates with USPS as a flat; a lumpy or thicker one rates as a package. Weigh it packed and check the current USPS rate. A 5 x 7 inch shipping label covers its face.
What is the difference between a bubble mailer and a mailer box?
Structure. A bubble mailer is a flexible envelope with an air film lining, so it protects against scuffing and short drops while conforming to whatever is inside. A mailer box has walls and a tuck-in lid, so it holds a shape on a shelf and takes full color printing across the outside; corrugated ones also resist crushing. The practical dividing line is whether the item can survive being pressed. Apparel, prints, and paperbacks go in a mailer. Anything with glass, a screen, a rigid corner, or an unboxing moment goes in a box.
Get Started
25 shipping labels cost $25, full color on 23 stocks
Start with a full color shipping label, add printed tape when the volume is there, and move to printed mailer boxes when the unboxing is part of the product.
Legal Disclaimer
Gold Standard guarantees apply to all standard orders placed through 4over4.com. Price match requires verifiable proof of a competitor's published price for an equivalent product with matching specifications and turnaround time. Satisfaction guarantee covers manufacturing defects and print quality issues. Contact support with order number and documentation.
