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16" x 21" Large Grey Mailing Bags (A2 Size) – Heavy Duty Shipping for Large Items & Bundles (pack of 25) 16" x 21" Large Grey Mailing Bags (A2 Size) – Heavy Duty Shipping for Large Items & Bundles (pack of 25) £3.50
25 x Grey Mailing Bags | 9" x 12" (229x305mm) | Royal Mail Large Letter A4 Size 25 x Grey Mailing Bags | 9" x 12" (229x305mm) | Royal Mail Large Letter A4 Size £2.50

12″ x 16″ Medium Grey Mailing Bags (A3 Size – 300mm x 400mm) – Ideal for Jumpers, Jeans & Shoe Boxes (Pack of 25)

£3.00

What Fits in This Bag?

  • Hoodies, chunky knitwear, and pairs of jeans.

  • Toddler and small adult shoe boxes.

  • Handbags and larger accessories.

  • Standard board games or multiple thin clothing items.

10 in stock

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12" x 16" Medium Grey Mailing Bags (A3 Size - 300mm x 400mm) – Ideal for Jumpers, Jeans & Shoe Boxes (Pack of 25)
12" x 16" Medium Grey Mailing Bags (A3 Size - 300mm x 400mm) – Ideal for Jumpers, Jeans & Shoe Boxes (Pack of 25)
£3.00
This item is selling fast!

Why Thousands of UK Sellers Choose Packaging365

  • Royal Mail & Evri Ready: All our bags and boxes are tested against UK courier dimensions to help you avoid unexpected surcharges.

  • Dispatched in 24 Hours: We know your customers are waiting. Orders placed before 2 PM are processed the same day for lightning-fast UK delivery.

  • Eco-Conscious Packaging: We prioritise 100% recyclable materials, helping your small business stay green without the high price tag.

  • No-Hassle Returns: Not the right size? No problem. We offer a 30-day money-back guarantee for all unused packaging

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When the 9×12 is just a bit too tight, the 12″ x 16″ (A3 equivalent) Medium Grey Mailing Bags are your go-to hero. This is our most popular “Medium” size, offering the extra room needed for bulkier clothing items and small shoe boxes. Lightweight but incredibly tough, these bags allow you to ship heavier textiles without the fear of the packaging splitting during transit.

Why Sellers Choose This Size:

  • Heavy Duty Strength: Our co-extruded polythene is puncture-resistant, meaning sharp corners on games or boxes won’t poke through.
  • The “Bundle” Bag: The perfect size for multi-item Vinted bundles that are too large for a standard mailer.
  • Professional Aesthetic: The clean, matte grey finish gives your brand a professional look compared to flimsy, transparent alternatives.
  • Tamper-Evident Security: Once the permanent seal is shut, it cannot be opened without leaving visible signs of tampering.

What Fits in This Bag?

  • Hoodies, chunky knitwear, and pairs of jeans.
  • Toddler and small adult shoe boxes.
  • Handbags and larger accessories.
  • Standard board games or multiple thin clothing items.

Additional information

Weight0.4 kg
Pack Size (Bags)

25

Colour

Grey

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Mailing Bags Size Guide

Packing a t-shirt in a grey mailing bag

Not sure which bag you need for your Vinted or eBay sales? Use our mailing bags size guide below to find the perfect fit for your items. All our bags are lightweight to help you stay within Royal Mail and Evri weight limits.

Quick Reference Chart

Bag Size (Inches)Metric Size (mm)Best For…Royal Mail Format
9 x 12″225 x 300 mmT-Shirts, Leggings, Thin Summer Dresses, A4 DocumentsLarge Letter (if < 25 mm thick)
12 x 16″300 x 400 mmThe “Workhorse”: Hoodies, Jeans, Coats, Small Shoe Boxes, Small BundlesSmall Parcel
16 x 21″400 x 525 mmWinter Coats, Boots, Larger Shoe Boxes, Multi-item “Bundles”Small/Medium Parcel

🧥 Which bag for my item?

  • T-Shirts & Tops: Most single t-shirts fit perfectly in a 9×12″ bag. If the fabric is very thin, you can often keep this under 2.5cm thick to post as a Large Letter, saving you nearly £2.00 in postage!
  • Jeans & Trousers: Adult jeans are bulky. We recommend the 12×16″ bag. It allows room for the denim to be folded without putting stress on the seams.
  • Hoodies & Knitwear: For a standard adult hoodie, go for the 12×16″. If it’s an extra-thick “oversized” hoodie or a winter coat, move up to the 16×21″.
  • Vinted Bundles: If a buyer has bought 3–5 items, the 16×21″ is your best friend. It’s heavy-duty and large enough to keep everything together in one secure package.

📏 Top Packing Tips for Sellers

  1. The “Air Squeeze”: Before sealing the bag, press down to remove excess air. This makes the parcel flatter and less likely to get caught in courier machinery.
  2. The Fold Test: If your item is right on the edge of two sizes, go for the larger one. You can always fold the excess plastic over and tape it down, but you can’t stretch a bag that’s too small!
  3. Check the Depth: Remember, Royal Mail “Large Letter” is about the thickness (25mm), not just the width. If your t-shirt is folded too “fat,” it will be charged as a Small Parcel.
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