# Rigid card mailers, 6 × 8 in, 100 pack > Stiff envelopes that keep cards flat in transit. - Mailers, Best value - Typical UK price: $35 to $50 (a typical band, not a live price) - Platforms: Whatnot, eBay, Vinted, TikTok Shop, Depop, Etsy - Orders a week: 0–2000 - Checked October 7, 2026 A sleeved and toploaded card in a rigid mailer stays flat through sorting machines and costs far less to ship than a box. ## Kit rankings - #3 in [Best poly mailers, bubble mailers and card mailers](https://sellersetups.com/us/kit/mailers) ## Setups - [Pro Whatnot streaming setup for card breaks](https://sellersetups.com/us/setups/pro-whatnot-streaming): A two-camera studio with app-controlled lights, a button pad for angles and a packing line, for card breakers shipping 80 to 300 orders a week. - [Whatnot card break setup for sports cards](https://sellersetups.com/us/setups/sports-card-breaks): An overhead rip camera, a sorting system for hits per buyer and flat mailer packing, for running baseball, basketball and football breaks on Whatnot and eBay. - [Whatnot card setup: starter kit](https://sellersetups.com/us/setups/whatnot-card-starter): Camera, lights and packing kit for running your first Whatnot card shows from a desk and shipping the orders next morning, on a starter budget. ## Who should keep rigid mailers in stock Card sellers shipping one to a handful of toploaded singles use these, and so does anyone sending photos, prints or postcards. Whatnot, eBay and TikTok Shop buyers all expect a card to arrive flat. A 100 pack at $35 to $50 covers a busy month for a breaker and a few months at a casual pace. If most of your orders are lots of 50 cards or more, a small box serves you better. ## Inner size, board and flap A 6 × 8 in mailer fits a 3 × 4 in toploader with room to spare, and two side by side in most cases. Read the listed inner size, as some rigid mailers are cut smaller than their outer size suggests. Choose stiff paperboard on both faces, ideally with a printed "Do not bend" line. A peel-and-seal flap saves you reaching for tape on every order. A rigid envelope does not bend, so USPS treats it differently from a flexible letter. Most card sellers buy a Ground Advantage label for it by weight; check USPS's current rules for letters and large envelopes before you price shipping. ## Packing a card order in under a minute Sleeve the card, load it into a toploader, seal the toploader in a team bag, then slide the bundle into the mailer. For two or three cards, lay the toploaders side by side, not stacked loose, and tape them together with painter's tape. Stick the label on the front, away from the flap, and weigh the finished envelope before you buy postage. A pocket scale reads light card orders to a fraction of an ounce. ## Padded mailers, boxes and poly mailers for cards Kraft bubble mailers, #0, 100 pack, are the fallback. They cushion bumps, but the bubble lining flexes, so add a piece of cardboard for any toploaded card. Small corrugated boxes, 25 pack, give bigger lots crush protection an envelope cannot match. Switch to a box once a card order gets too thick to lie flat. Poly mailers suit clothing, but they let cards bend, so don't use them for card orders. ## Mailer cost against a $5 card sale At $35 to $50 per 100, the mailer adds about 35 to 50 cents per order. With a sleeve, toploader and team bag, a full card pack still comes in under 75 cents before postage. That leaves room on a $5 to $10 card sale. Track your costs per order for a month to see whether a bigger pack brings the mailer price down enough to pay off. ## Common mistakes - Toploader every card before it goes in, because a bare card bends at the corners. - Two toploaders stacked on top of each other make a thick, lumpy envelope that snags in machines; lay them side by side. - A label over the flap means the buyer tears through it. Place it on the plain front. - A guessed weight can mean underpaid postage and an adjustment charge, so weigh each finished mailer. - Mailers cut smaller than their stated size jam toploaders in tight; check the inner dimensions before you order a big pack. ## Guides - [How to run soccer card breaks on Whatnot](https://sellersetups.com/us/guides/football-card-breaks): Running Premier League, MLS and Champions League card breaks on Whatnot: picking a format, filling spots, ripping on camera and shipping each buyer's cards. - [How to ship Pokémon cards in the US](https://sellersetups.com/us/guides/how-to-post-pokemon-cards): Penny sleeve, toploader, team bag and a rigid mailer: the layers that get a Pokémon single to a US buyer flat, plus when an envelope stops being enough. - [Whatnot fees, Poshmark and eBay: what sellers keep](https://sellersetups.com/us/guides/reseller-earnings-maths): US fees on Whatnot, Poshmark and eBay, worked examples of profit per item after shipping and packaging, and the levers that change what you take home. - [How to sell Pokémon cards: live setup and kit](https://sellersetups.com/us/guides/sell-pokemon-cards-live): The camera, light, sound and card protection you need to sell Pokémon cards live, and the order to buy it in. ## Questions ### Can I ship a rigid mailer with a stamp as a letter? Usually not. USPS letter pricing expects a flexible envelope, and a rigid one can come back for more postage. Buy a package label by weight, and check USPS's current rules if you want letter rates. ### How many toploaders fit in one 6 × 8 in mailer? Two side by side fit in most. Stacking more raises the thickness, so measure the result. ### Do I need a bubble mailer instead? Not for single cards. Bends damage a card more than knocks do, and the stiff board resists bending. Use padding for odd-shaped items. ### Can I write "Do not bend" on a plain envelope instead? You can, but sorting machines ignore it. The board keeps the card flat. ### Will a rigid mailer fit a graded slab? A slab is too thick for most card mailers. Ship slabs in a small box with padding.