Grey Mailing Bags 9×12" (229×305 mm) – reliable A4 mailing bags made from 60 µm recycled LDPE. These self-seal postal bags are moisture-proof / water-resistant, fully opaque for privacy, and ideal for eBay, Amazon, and Shopify sellers shipping A4 documents, clothing or small parcels daily.
Grey Mailing Bags 9×12" (229×305 mm) – the smart A4-friendly choice for daily post
These 9×12" grey poly mailers are one of the UK’s most popular A4 packaging sizes. Built from 60-micron co-extruded recycled LDPE, they combine strength, flexibility and moisture protection. The smooth grey finish ensures clean presentation and complete privacy from packing bench to customer doorstep.
Need a different fit? See all Grey sizes or explore the full Mailing Bags range. Prefer a branded look? Check out Coloured Mailing Bags.
Why this 9×12" size works so well
This size fits A4 documents with room for padding or small apparel without wasting space. Perfect for single T-shirts, diaries, planners, thin jumpers, and beauty boxes. The compact footprint saves storage space and keeps postage within Royal Mail Small Parcel limits.
Who it’s for
- Apparel & merch: single T-shirts, gym wear, kids’ clothing, scarves, socks.
- Beauty & wellness: boxed skincare, cosmetics, hair accessories, nail kits.
- Stationery & print: A4 brochures, photo books, diaries, planners.
- Craft & hobby: fabric cuts, sewing patterns, kits, components in sleeves.
- Marketplace sellers: quick, reliable packaging for high-turnover A4 parcels.
Fit & packing guidance
- Best fit: A4 items, T-shirts, diaries, boxed cosmetics, or soft goods.
- If it’s tight: step up to 10×14" for thicker books or bulky clothing.
- If it’s roomy: use a paper or bubble inner sleeve for a tighter fit.
- Corner care: pad sharp corners to prevent punctures.
- Press out air: flatten before sealing to keep parcels neat and postal-friendly.
Key benefits
- Peel & seal closure – fast, tamper-evident and reliable.
- 60-micron co-extruded film resists splits, scuffs and rough handling.
- Moisture-proof / water-resistant for dependable all-weather delivery.
- Opaque grey finish for privacy and a professional appearance.
- Lightweight design helps lower postage and storage costs.
- Recyclable LDPE – remove adhesive strip before recycling.
Eco & Materials
Material: 100% recycled LDPE (code 4), co-extruded for durability and opacity. Recyclable through UK soft-plastic return points. Not biodegradable or compostable, but has a reduced carbon footprint compared with virgin plastic.
Strength & Protection
60 µm co-extruded film gives strong tear and puncture resistance while staying flexible. The tamper-evident self-seal strip locks instantly, securing items through sorting and transit. The grey film ensures full opacity and privacy.
Storage & Performance
Store flat between 13–21 °C, away from sunlight or heat. Allow stock to reach room temperature before use to maintain adhesive strength and reliable sealing.
Lightweight = Lower Postage
These recycled LDPE mailers are ultra-lightweight and space-saving — helping businesses stay within Royal Mail Small Parcel or Evri low-weight brackets while maintaining a professional look.
Size comparison (choose the best fit)
| Size | Inches | Millimetres | Typical fit |
|---|---|---|---|
| Smaller option | 6.5 × 9" | 165 × 229 mm | A5 packs, small accessories, boxed cosmetics |
| This page | 9 × 12" | 229 × 305 mm | A4 with room, T-shirts, diaries, slim boxes |
| Larger option | 10 × 14" | 254 × 355 mm | Books, thicker apparel, multi-item parcels |
If you ship mixed parcel sizes, keep 10×14" and 12×16" alongside this size for flexibility during busy periods.
Buying guide: choosing the right grey mailing bag size
Selecting the right mailing bag size helps reduce postage costs and wasted materials. A 6.5×9" bag works best for A5 parcels and accessories, while a 9×12" bag fits A4 documents, books and single T-shirts with space for padding. For thicker apparel or multiple items, move up to 10×14" to stay within Royal Mail Small Parcel limits. Always flatten air before sealing and store mailers flat for the best seal and appearance.
Packing tips to save time and reduce damages
- Use a light inner sleeve for sharp or dusty goods.
- Fold garments neatly to avoid corner stress.
- Flatten air pockets before sealing for clean labels and scanning.
- Place invoices in a document wallet on the outside.
Build a complete packing setup
Pair your grey mailing bags 9×12" with packaging tape for inner boxes, document wallets for paperwork, and cardboard boxes for fragile goods. Explore all Mailing Bags and Coloured Mailing Bags for matching brand options.
Common searches: grey poly mailers, A4 postal bags, self-seal mailing bags, recycled LDPE mailers UK, small parcel packaging.
| Material | LDPE (code 4) |
| Size | 9x12 Inch (229x305 mm) |
| Color | Grey |
| Closure | Peel-and-Seal (Permanent) |
| Recyclability | Return to Supermarket Soft-Plastic Points |
| Thickness | 60 µm |
| Water Protection | Water-Resistant |
What fits in a 9×12" grey mailing bag?
Is the 9×12" bag strong enough for daily use?
Are these grey mailing bags waterproof?
Are 9×12" grey mailing bags recyclable?
Are the bags fully opaque for privacy?
Will 9×12" work with Royal Mail and couriers?
When should I choose 9×12" over 10×14"?
How should I store 9×12" mailing bags?
Do they have a strong seal?
Any packing tips for best results?
Royal Mail 24 Tracked
Dispatched same day if ordered before 5 pm Monday to Friday. Please allow up to 1-2 days for delivery.
£1.99
DPD Next Day
Dispatched same day if ordered before 3 pm Monday to Thursday. Not available to Scottish Highlands & Islands.
£4.99
Free on orders over £100