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.

Wholesale Mailing Bags for High-Volume Businesses

These 9×12" grey mailing bags are supplied in trade quantities and are ideal for businesses dispatching small parcels, documents, accessories and lightweight products every day. Widely used by e-commerce sellers, fulfilment centres, online retailers, Amazon sellers, eBay businesses and Shopify stores, they offer a cost-effective solution for high-volume order fulfilment.

Each box contains 3,000 mailing bags, helping businesses achieve lower packaging costs per order, reduce stock replenishment frequency and maintain efficient dispatch operations throughout the year.

The versatile 9×12" size is perfect for T-shirts, documents, books, stationery, phone accessories, cosmetics, small fashion items and other compact products. Whether you're shipping hundreds of parcels each week or processing large daily order volumes, buying in bulk provides excellent value, faster packing and a more efficient warehouse workflow.

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)

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.