Grey Mailing Bags 21×24" (533×610 mm) give generous space for bedding sets, pillows, bulky textiles and mid-to-large retail boxes while keeping parcels lightweight. Made from tough 60 µm co-extruded, 100% recycled LDPE, they are moisture-proof / water-resistant, fully opaque for privacy and recyclable via UK soft-plastic schemes. At this size, most loads route as Royal Mail Medium Parcel or by couriers (Evri, DPD, Yodel) — check limits on the Royal Mail size guide.
Need a different fit? See all Grey sizes or browse the full Mailing Bags range. Prefer brand colour? Explore Coloured Mailing Bags.
Why this 21×24" size?
When 17×24" starts to strain, 21×24" adds height for duvet covers, pillows, apparel bundles and larger boxed gifts — without jumping to rigid cartons. Need more width than height? Try 20×26" (wider, slightly shorter).
Real use examples (what typically fits)
- Textiles & home: bedding sets, pillows, throws, towel bundles, large cushion covers.
- Apparel: coats, knitwear bundles, multi-item clothing stacks.
- Boxed goods: mid-to-large retail boxes and gift sets with a light inner wrap.
Fit & packing guidance
- Best fit: bedding/textiles, stacked apparel, larger boxed kits.
- Need more width? Use 20×26".
- Need less bulk? Step down to 17×24" for a neater seal and lower postage.
- Corner care: pad sharp inner-box edges to reduce punctures.
- Press out air: flatten before sealing so labels sit flat and sacks/totes stack cleanly.
Key benefits
- Fast self-seal, tamper-evident closure — no tape needed for most orders.
- 60 µm co-extruded film — resists tears, splits and scuffs in courier handling.
- Moisture-proof / water-resistant protection for wet routes.
- Fully opaque grey — privacy and a clean, professional look on delivery.
- Lightweight — helps keep costs down versus rigid cartons.
- Recyclable LDPE (code 4) — remove the glue strip before recycling.
Eco & materials
Material: 100% recycled LDPE (code 4), co-extruded for strength and opacity. Recyclable at many UK supermarket soft-plastic return points. Not biodegradable or compostable.
Strength & protection
The 60 µm film gives dependable puncture and tear resistance on bulky loads. The permanent adhesive forms a tamper-evident bond once pressed, protecting contents through warehouse and courier networks.
Storage & performance
Store flat at 13–21 °C away from heat/sunlight. Let cold stock reach room temperature before use for consistent seal strength.
Lightweight = lower postage
Mailing bags cut dead weight and reduce parcel size vs boxes. At 21×24", many shipments route as Royal Mail Medium Parcel or via couriers; check service limits before dispatch.
Size comparison (choose the right bag)
| Size | Inches | Millimetres | Typical fit |
|---|---|---|---|
| Step down | 17×24" | 432×610 mm | Bedding sets, bulky textiles, larger kits |
| This page | 21×24" | 533×610 mm | Pillows, throws, multi-item apparel, bigger boxes |
| Wider option | 20×26" | 508×660 mm | Wider boxed goods, large textiles |
| Step up | 24×36" | 610×914 mm | Very large textiles and retail boxes |
Buying guide: 17×24", 20×26" or 21×24"?
17×24" handles bedding sets and big apparel bundles. Choose 21×24" when you need extra height for pillows/duvets. Pick 20×26" if your loads are wider boxed goods where width matters more than height. For very large items, step up to 24×36".
Common searches
21×24 mailing bags • extra-large grey poly mailers • waterproof postal bags • recyclable mailing bags UK • Royal Mail Medium Parcel packaging • bulk grey mailing bags • eBay and Amazon shipping bags
| Material | LDPE (code 4) |
| Size | 21x24 Inch (533x610 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 21×24" grey mailing bag?
Is 21×24" suitable for Royal Mail services?
Are these grey mailing bags waterproof?
Are 21×24" grey mailing bags recyclable?
How strong are they for heavy textiles?
When should I pick 21×24" over 20×26"?
When should I step down to 17×24"?
Are the bags fully opaque for privacy?
How should I store 21×24" mailing bags?
Do I need extra tape with 21×24" bags?
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