Why this exists
Before this was a product, it was a daily annoyance. Selling singles and lots as UntaintedMagicShop on eBay and TCGplayer means shipping cards every single day, and every option had the same trade-offs: toploaders in an envelope go rigid and trigger the non-machinable surcharge (or get bumped to package rates), plain white envelopes leave cards rattling around unprotected, and bubble mailers eat $4–5 of margin on a $10 order.
The envelope we wanted didn't exist — so we designed it. A standard #10 body in water-resistant stock with a 3-pocket card strip built into the envelope itself: cards sit in pockets instead of loose, the loaded piece stays under 1/4" thick and flexes through USPS automation, and there's nothing to assemble, tape, or cut. It's now patent-pending.