The Complete Guide to Mailer Boxes: 7 Styles, Flute Types, Sizing & Price Benchmarks
A mailer box is the self-locking corrugated box that ships your product and presents it in the same package — no outer carton, no tape, no plain brown anonymity. This guide covers every type we manufacture, the flutes and closing styles behind them, standard sizes, and what each format actually costs direct from the factory.
The 7 Mailer Box Types
Every mailer box we produce belongs to one of seven construction families. The family decides how the box folds, closes, protects, and presents — start here, then go deep on the type that fits your product.
Tuck-Top Mailer Boxes (RETF)
The classic roll-end tuck front mailer. Self-locking, tape-free, and the default choice for general e-commerce.
From $0.52/ea →
Peel-and-Seal Mailer Boxes
Self-adhesive strip closure with a tear-strip opening. The fastest pack on the bench and tamper-evident by design.
From $0.58/ea →
Die-Cut Mailer Boxes
Precision-cut custom shapes, windows, and locking contours for products that do not fit standard geometry.
From $0.72/ea →
Flat Mailer Boxes
Slim low-profile mailers for prints, books, documents, and flat goods — the lowest DIM weight in the range.
From $0.39/ea →
Rigid Magnetic Mailer Boxes
Luxury rigid board with a concealed magnetic snap. The presentation format for premium and gift programs.
From $1.85/ea →
Apparel Sleeve Mailer Boxes
A rigid inner tray with a printed slide-off sleeve — boutique apparel presentation that ships like a mailer.
From $0.76/ea →
Mailer Boxes with Inserts
Die-cut partitions and foam inserts that hold bottles, jars, and kits in a fixed, retail-ready layout.
From $0.85/ea →Not Sure Which Type?
Work through the four-step selection method at the end of this guide, or compare styles side by side in our shipping guide.
Style Selection Guide →More Formats in the Range
Running a Subscription Box Program?
Standing dielines, seasonal artwork swaps, and stored color profiles — your monthly box, reordered in one email and identical every cycle from $0.58/ea.
Subscription Mailer Boxes →Need a Fully Custom Mailer?
Your exact size, board, flute, and full CMYK print inside and out — engineered on a free CAD dieline within 24 hours, direct from the factory floor from $0.48/ea.
Custom Mailer Boxes →Flutes: E-Flute vs B-Flute
The flute is the wavy layer inside the corrugated board, and it decides the trade-off between print quality and raw strength. Two grades cover nearly every mailer program.
E-Flute — 1.5mm (1/16") Micro-Flute
The mailer standard. Its tight flute profile produces the smoothest print surface for CMYK artwork, keeps the folded box slim for lower DIM weight, and still delivers ECT-32 crush resistance for typical e-commerce loads.
B-Flute — 3mm (1/8") Standard Flute
The strength grade. Taller flute arches (ECT-44 board) absorb stacking pressure and drop impact for heavier or fragile contents, at a slightly coarser print surface and a thicker folded profile.
Full engineering comparison: E-Flute vs B-Flute — which does your brand need? · Board and finish options: Materials & Finishes Guide
Carrier Compatibility: Royal Mail PiP & USPS
A mailer box earns its keep inside carrier pricing bands. Corrugated mailers are rigid parcels in the US — but in the UK, slim E-flute formats can qualify for Royal Mail's Pricing in Proportion (PiP) letter bands, the single biggest postage saving available to small-goods brands.
| Carrier Band | Max Dimensions | Max Weight | Which Mailers Fit |
|---|---|---|---|
| USPS — Standard Parcels | Length + girth ≤ 108" | 70 lbs | All standard mailer footprints ship as regular parcels; keep length under 22" to avoid Ground Advantage dimension fees, and watch DIM weight over 1 cubic foot. |
| Royal Mail PiP — Large Letter | 353 × 250 × 25mm | 750g | Slim E-flute flat mailers and mini formats under 25mm thick ship at letter rates, not parcel rates. |
| Royal Mail PiP — Small Parcel | 450 × 350 × 160mm | 2kg | Nearly every standard footprint in our sizes chart, including the 12" × 9" × 4" apparel standard. |
| Royal Mail PiP — Medium Parcel | 610 × 460 × 460mm | 20kg | Oversized gift crates, bulk retail packs, and multi-item wholesale cartons. |
Design rule: pick your carrier band first, then your box. A product that fits a 25mm E-flute flat mailer in the UK posts for a fraction of parcel pricing — and in the US, staying right-sized keeps DIM-weight billing at bay. Both are decided at the dieline stage, which is why our engineers start every quote from your destination carrier.
Closing Styles
Roll-End Tuck Front (RETF)
The lid tucks into the front wall and locks mechanically — zero tape, clean lines. Tuck-top mailers
Peel-and-Seal Adhesive
A pre-applied hot-melt strip seals in one press and opens by tear strip — the fastest, tamper-evident close. Peel-and-seal mailers
Self-Locking Die-Cut Tabs
Interlocking tabs cut into the sheet itself hold custom shapes shut without any added material. Die-cut mailers
Magnetic Snap & Sleeve
Concealed magnets or a slide-off printed sleeve — presentation closures for premium programs. Rigid magnetic · Apparel sleeve
Sizes at a Glance
Twelve standard footprints cover most e-commerce shipments. The three most-ordered:
9" × 6" × 3" — The Small Standard
162 cu in · 1.2 lbs DIM — small apparel, books, wellness kits.
10" × 8" × 4" — The Subscription Standard
320 cu in · 2.3 lbs DIM — the classic curated-box footprint.
12" × 9" × 4" — The Apparel Standard
432 cu in · 3.1 lbs DIM — footwear, hoodies, large gift sets.
Full reference: Standard mailer box sizes chart · Sizing method: How to choose the right size
Mailer Box Price Ranges
Factory-direct starting prices across the full range — per unit at volume tiers, 500-unit minimum per design. What moves a specific quote up or down is broken down in the mailer box cost guide — and the MOQ explainer covers why the 500-unit minimum exists.
| Style | From | Best For |
|---|---|---|
| Mini Mailer Boxes | $0.34/ea | Jewelry, samples & small accessories |
| Flat Mailer Boxes | $0.39/ea | Prints, books & documents |
| Wholesale Mailer Boxes | $0.40/ea | Bulk & recurring programs |
| Kraft Corrugated Mailer Boxes | $0.42/ea | Eco-positioned brands |
| Custom Shipping Boxes (RSC) | $0.44/ea | Heavy outer shipping cartons |
| Stationery Shipping Boxes | $0.46/ea | Books, planners & paper goods |
| Custom Mailer Boxes | $0.48/ea | General custom e-commerce |
| Tuck-Top Mailer Boxes | $0.52/ea | The all-round e-commerce default |
| Peel-and-Seal Mailer Boxes | $0.58/ea | Fast, tamper-evident packing |
| Subscription Mailer Boxes | $0.58/ea | Monthly & quarterly box programs |
| Printed Mailer Boxes | $0.64/ea | Full-color branded unboxing |
| Die-Cut Mailer Boxes | $0.72/ea | Custom shapes & windows |
| Apparel Sleeve Mailer Boxes | $0.76/ea | Boutique apparel presentation |
| Matte Black Mailer Boxes | $0.78/ea | Luxury dark-finish unboxing |
| Mailer Boxes with Inserts | $0.85/ea | Fragile kits & arranged layouts |
| Rigid Magnetic Mailer Boxes | $1.85/ea | Premium gift & presentation |
How to Choose Your Mailer Box in 4 Steps
Start With the Product
Weight, fragility, and shape pick the family: flat goods to flat mailers, fragile kits to inserts, premium products to rigid magnetic. See the style selection guide for the full comparison.
Size It Right
Match internal dimensions to your product plus protection room — every wasted inch is DIM-weight freight cost on every order.
Pick Flute & Board
E-flute for print-led programs, B-flute for heavy or fragile loads; kraft or white board sets the base look before printing.
Decide the Print
Plain, one-color, or full CMYK inside and out — print is where a shipping box becomes your cheapest marketing channel.
Configure Your Custom Mailer Boxes
Wholesale tiered pricing directly from the packaging floor. Receive an engineering review and guaranteed quote within 2–4 business hours.
Quote Request Received by Packaging Engineering
We are preparing your custom dieline template and wholesale volume rate breakdown. A packaging specialist will contact you at within 2–4 business hours.
Frequently Asked Factory & Manufacturing Questions
Transparent answers on minimums, production timelines, dielines, and corrugated board specifications.
What is a mailer box?
A mailer box is a self-locking corrugated cardboard box designed to ship products directly through parcel and postal networks without an outer shipping carton. Unlike a standard RSC shipping box, a mailer is presentation-grade: it folds from a single die-cut sheet, locks without tape, and is printed inside and out as the customer-facing unboxing.
What size mailer box do I need?
Measure your product, add roughly half an inch of protection room on each dimension, and match the result against a standard footprint — the full chart of internal dimensions, volumes, and DIM weights is in our standard mailer box sizes chart. If nothing standard fits, a custom dieline is cut to your exact product at no engineering fee.
Should I choose E-flute or B-flute for my mailer boxes?
E-flute (1/16 inch) is the default for mailer boxes: its fine flute profile gives the smoothest print surface and keeps the box slim for DIM weight. Choose B-flute (1/8 inch) when loads are heavy, contents are fragile, or boxes will be stacked in storage — it trades a little print smoothness for significantly more crush strength.
How much do mailer boxes cost?
Factory-direct mailer boxes run from $0.34/ea for mini formats to $1.85/ea for rigid magnetic presentation boxes, with most e-commerce styles between $0.39 and $0.85 at volume. The minimum order is 500 units per design, and the steepest per-unit savings happen between the 500 and 2,500 unit tiers — the full breakdown is in our mailer box cost guide.
Have a technical question about burst test ratings or dieline fitment?
Consult directly with a packaging engineer via email at sales@mailerboxfactory.com or configure your specs in our Quote Configurator.