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Grey Mailing Bags | 12 x 16 Inch | Small Parcel Size Grey Mailing Bags | 12 x 16 Inch | Small Parcel Size £2.99 – £28.99Price range: £2.99 through £28.99
Grey Mailing Bags | 6 x 9 Inch | Royal Mail Large Letter A5 Size Grey Mailing Bags | 6 x 9 Inch | Royal Mail Large Letter A5 Size £1.49 – £13.29Price range: £1.49 through £13.29

Grey Mailing Bags | 16 x 21 Inch | Medium Parcel Size

Professional A3 Shipping Solutions – 16″ x 21″ (400mm x 525mm) Grey Mailing Bags

  • What Fits in This Bag?

        • Winter Wear: Puffer jackets, heavy overcoats, and chunky wool knitwear.

        • Footwear: Large adult shoeboxes or multiple pairs of trainers.

        • Home Goods: Single duvets, throw pillows, or complete bedding sets.

        • The “Mega Bundle”: The perfect solution for Vinted or eBay sellers shipping several items of clothing in a single transaction.
        • E-Commerce: Ideal for eBay, Vinted, Depop, and Etsy sellers shipping non-fragile items.

    Also available in our mixed size packs

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    Grey Mailing Bags | 16 x 21 Inch | Medium Parcel Size
    Grey Mailing Bags | 16 x 21 Inch | Medium Parcel Size
    £3.99 – £36.99Price range: £3.99 through £36.99
    Total: £0.00
    🚚
    Same-Day Dispatch
    Orders before 1pm
    📦
    Postal Approved
    Royal Mail & Small Parcel
    🛡️
    Heavy-Duty Poly
    Tear-resistant & recyclable
    Guaranteed Safe Checkout

    Professional Shipping Solutions – 16″ x 21″ Grey Mailing Bags

    Stop struggling with small bags that split at the seams. Our 16″ x 21″ Large Grey Mailing Bags are the “Large Parcel” heroes of our range. Specifically designed for the “bulky” side of reselling, these bags are essential for shipping heavy winter wear, boxed footwear, or large multi-item bundles.

    Engineered from premium, co-extruded polythene, these bags offer superior puncture resistance, ensuring that even sharp box corners won’t break through during the rough-and-tumble of UK courier sorting centers.

    Why Sellers Love the 16×21 Size:

    • Built for Bulk: The generous capacity easily accommodates larger items that standard mailers can’t touch.
    • Heavy-Duty Security: Featuring a high-tack, permanent “peel and seal” strip. Once shut, it stays shut until your customer cuts it open.
    • 100% Opaque & Discreet: Opaque grey mailing bags offer total privacy for high-value contents, from designer boots to electronics.
    • Weather-Proof Protection: Rain stays out and your products stay dry, providing professional peace of mind for every shipment.
    • Tear-Resistant Technology: Flexible yet incredibly strong, these bags are built to handle the weight of heavy textiles without failing.

    What Fits in This Bag?

    • Winter Wear: Puffer jackets, heavy overcoats, and chunky wool knitwear.
    • Footwear: Large adult shoeboxes or multiple pairs of trainers.
    • Home Goods: Single duvets, throw pillows, or complete bedding sets.
    • The “Mega Bundle”: The perfect solution for Vinted or eBay sellers shipping several items of clothing in a single transaction.

    Also available in our mixed size packs

    Technical Specifications:

    • Size: 16 x 21 inches (400mm x 525mm approx)
    • Material: 100% Recyclable LDPE (60 Micron thickness)
    • Closure: Permanent Self-Seal Strip
    • Color: Professional Opaque Grey

    Additional information

    Weight0.525 kg

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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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